| Step | Hyp | Ref | Expression | 
						
							| 1 |  | xpsff1o.f | ⊢ 𝐹  =  ( 𝑥  ∈  𝐴 ,  𝑦  ∈  𝐵  ↦  { 〈 ∅ ,  𝑥 〉 ,  〈 1o ,  𝑦 〉 } ) | 
						
							| 2 |  | xpsfrnel2 | ⊢ ( { 〈 ∅ ,  𝑥 〉 ,  〈 1o ,  𝑦 〉 }  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ↔  ( 𝑥  ∈  𝐴  ∧  𝑦  ∈  𝐵 ) ) | 
						
							| 3 | 2 | biimpri | ⊢ ( ( 𝑥  ∈  𝐴  ∧  𝑦  ∈  𝐵 )  →  { 〈 ∅ ,  𝑥 〉 ,  〈 1o ,  𝑦 〉 }  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) ) | 
						
							| 4 | 3 | rgen2 | ⊢ ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐵 { 〈 ∅ ,  𝑥 〉 ,  〈 1o ,  𝑦 〉 }  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) | 
						
							| 5 | 1 | fmpo | ⊢ ( ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐵 { 〈 ∅ ,  𝑥 〉 ,  〈 1o ,  𝑦 〉 }  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ↔  𝐹 : ( 𝐴  ×  𝐵 ) ⟶ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) ) | 
						
							| 6 | 4 5 | mpbi | ⊢ 𝐹 : ( 𝐴  ×  𝐵 ) ⟶ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) | 
						
							| 7 |  | 1st2nd2 | ⊢ ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  →  𝑧  =  〈 ( 1st  ‘ 𝑧 ) ,  ( 2nd  ‘ 𝑧 ) 〉 ) | 
						
							| 8 | 7 | fveq2d | ⊢ ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  →  ( 𝐹 ‘ 𝑧 )  =  ( 𝐹 ‘ 〈 ( 1st  ‘ 𝑧 ) ,  ( 2nd  ‘ 𝑧 ) 〉 ) ) | 
						
							| 9 |  | df-ov | ⊢ ( ( 1st  ‘ 𝑧 ) 𝐹 ( 2nd  ‘ 𝑧 ) )  =  ( 𝐹 ‘ 〈 ( 1st  ‘ 𝑧 ) ,  ( 2nd  ‘ 𝑧 ) 〉 ) | 
						
							| 10 |  | xp1st | ⊢ ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  →  ( 1st  ‘ 𝑧 )  ∈  𝐴 ) | 
						
							| 11 |  | xp2nd | ⊢ ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  →  ( 2nd  ‘ 𝑧 )  ∈  𝐵 ) | 
						
							| 12 | 1 | xpsfval | ⊢ ( ( ( 1st  ‘ 𝑧 )  ∈  𝐴  ∧  ( 2nd  ‘ 𝑧 )  ∈  𝐵 )  →  ( ( 1st  ‘ 𝑧 ) 𝐹 ( 2nd  ‘ 𝑧 ) )  =  { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ) | 
						
							| 13 | 10 11 12 | syl2anc | ⊢ ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  →  ( ( 1st  ‘ 𝑧 ) 𝐹 ( 2nd  ‘ 𝑧 ) )  =  { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ) | 
						
							| 14 | 9 13 | eqtr3id | ⊢ ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  →  ( 𝐹 ‘ 〈 ( 1st  ‘ 𝑧 ) ,  ( 2nd  ‘ 𝑧 ) 〉 )  =  { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ) | 
						
							| 15 | 8 14 | eqtrd | ⊢ ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  →  ( 𝐹 ‘ 𝑧 )  =  { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ) | 
						
							| 16 |  | 1st2nd2 | ⊢ ( 𝑤  ∈  ( 𝐴  ×  𝐵 )  →  𝑤  =  〈 ( 1st  ‘ 𝑤 ) ,  ( 2nd  ‘ 𝑤 ) 〉 ) | 
						
							| 17 | 16 | fveq2d | ⊢ ( 𝑤  ∈  ( 𝐴  ×  𝐵 )  →  ( 𝐹 ‘ 𝑤 )  =  ( 𝐹 ‘ 〈 ( 1st  ‘ 𝑤 ) ,  ( 2nd  ‘ 𝑤 ) 〉 ) ) | 
						
							| 18 |  | df-ov | ⊢ ( ( 1st  ‘ 𝑤 ) 𝐹 ( 2nd  ‘ 𝑤 ) )  =  ( 𝐹 ‘ 〈 ( 1st  ‘ 𝑤 ) ,  ( 2nd  ‘ 𝑤 ) 〉 ) | 
						
							| 19 |  | xp1st | ⊢ ( 𝑤  ∈  ( 𝐴  ×  𝐵 )  →  ( 1st  ‘ 𝑤 )  ∈  𝐴 ) | 
						
							| 20 |  | xp2nd | ⊢ ( 𝑤  ∈  ( 𝐴  ×  𝐵 )  →  ( 2nd  ‘ 𝑤 )  ∈  𝐵 ) | 
						
							| 21 | 1 | xpsfval | ⊢ ( ( ( 1st  ‘ 𝑤 )  ∈  𝐴  ∧  ( 2nd  ‘ 𝑤 )  ∈  𝐵 )  →  ( ( 1st  ‘ 𝑤 ) 𝐹 ( 2nd  ‘ 𝑤 ) )  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ) | 
						
							| 22 | 19 20 21 | syl2anc | ⊢ ( 𝑤  ∈  ( 𝐴  ×  𝐵 )  →  ( ( 1st  ‘ 𝑤 ) 𝐹 ( 2nd  ‘ 𝑤 ) )  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ) | 
						
							| 23 | 18 22 | eqtr3id | ⊢ ( 𝑤  ∈  ( 𝐴  ×  𝐵 )  →  ( 𝐹 ‘ 〈 ( 1st  ‘ 𝑤 ) ,  ( 2nd  ‘ 𝑤 ) 〉 )  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ) | 
						
							| 24 | 17 23 | eqtrd | ⊢ ( 𝑤  ∈  ( 𝐴  ×  𝐵 )  →  ( 𝐹 ‘ 𝑤 )  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ) | 
						
							| 25 | 15 24 | eqeqan12d | ⊢ ( ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  ∧  𝑤  ∈  ( 𝐴  ×  𝐵 ) )  →  ( ( 𝐹 ‘ 𝑧 )  =  ( 𝐹 ‘ 𝑤 )  ↔  { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 }  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ) ) | 
						
							| 26 |  | fveq1 | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 }  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 }  →  ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ‘ ∅ )  =  ( { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ‘ ∅ ) ) | 
						
							| 27 |  | fvex | ⊢ ( 1st  ‘ 𝑧 )  ∈  V | 
						
							| 28 |  | fvpr0o | ⊢ ( ( 1st  ‘ 𝑧 )  ∈  V  →  ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ‘ ∅ )  =  ( 1st  ‘ 𝑧 ) ) | 
						
							| 29 | 27 28 | ax-mp | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ‘ ∅ )  =  ( 1st  ‘ 𝑧 ) | 
						
							| 30 |  | fvex | ⊢ ( 1st  ‘ 𝑤 )  ∈  V | 
						
							| 31 |  | fvpr0o | ⊢ ( ( 1st  ‘ 𝑤 )  ∈  V  →  ( { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ‘ ∅ )  =  ( 1st  ‘ 𝑤 ) ) | 
						
							| 32 | 30 31 | ax-mp | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ‘ ∅ )  =  ( 1st  ‘ 𝑤 ) | 
						
							| 33 | 26 29 32 | 3eqtr3g | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 }  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 }  →  ( 1st  ‘ 𝑧 )  =  ( 1st  ‘ 𝑤 ) ) | 
						
							| 34 |  | fveq1 | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 }  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 }  →  ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ‘ 1o )  =  ( { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ‘ 1o ) ) | 
						
							| 35 |  | fvex | ⊢ ( 2nd  ‘ 𝑧 )  ∈  V | 
						
							| 36 |  | fvpr1o | ⊢ ( ( 2nd  ‘ 𝑧 )  ∈  V  →  ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ‘ 1o )  =  ( 2nd  ‘ 𝑧 ) ) | 
						
							| 37 | 35 36 | ax-mp | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 } ‘ 1o )  =  ( 2nd  ‘ 𝑧 ) | 
						
							| 38 |  | fvex | ⊢ ( 2nd  ‘ 𝑤 )  ∈  V | 
						
							| 39 |  | fvpr1o | ⊢ ( ( 2nd  ‘ 𝑤 )  ∈  V  →  ( { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ‘ 1o )  =  ( 2nd  ‘ 𝑤 ) ) | 
						
							| 40 | 38 39 | ax-mp | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 } ‘ 1o )  =  ( 2nd  ‘ 𝑤 ) | 
						
							| 41 | 34 37 40 | 3eqtr3g | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 }  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 }  →  ( 2nd  ‘ 𝑧 )  =  ( 2nd  ‘ 𝑤 ) ) | 
						
							| 42 | 33 41 | opeq12d | ⊢ ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 }  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 }  →  〈 ( 1st  ‘ 𝑧 ) ,  ( 2nd  ‘ 𝑧 ) 〉  =  〈 ( 1st  ‘ 𝑤 ) ,  ( 2nd  ‘ 𝑤 ) 〉 ) | 
						
							| 43 | 7 16 | eqeqan12d | ⊢ ( ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  ∧  𝑤  ∈  ( 𝐴  ×  𝐵 ) )  →  ( 𝑧  =  𝑤  ↔  〈 ( 1st  ‘ 𝑧 ) ,  ( 2nd  ‘ 𝑧 ) 〉  =  〈 ( 1st  ‘ 𝑤 ) ,  ( 2nd  ‘ 𝑤 ) 〉 ) ) | 
						
							| 44 | 42 43 | imbitrrid | ⊢ ( ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  ∧  𝑤  ∈  ( 𝐴  ×  𝐵 ) )  →  ( { 〈 ∅ ,  ( 1st  ‘ 𝑧 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑧 ) 〉 }  =  { 〈 ∅ ,  ( 1st  ‘ 𝑤 ) 〉 ,  〈 1o ,  ( 2nd  ‘ 𝑤 ) 〉 }  →  𝑧  =  𝑤 ) ) | 
						
							| 45 | 25 44 | sylbid | ⊢ ( ( 𝑧  ∈  ( 𝐴  ×  𝐵 )  ∧  𝑤  ∈  ( 𝐴  ×  𝐵 ) )  →  ( ( 𝐹 ‘ 𝑧 )  =  ( 𝐹 ‘ 𝑤 )  →  𝑧  =  𝑤 ) ) | 
						
							| 46 | 45 | rgen2 | ⊢ ∀ 𝑧  ∈  ( 𝐴  ×  𝐵 ) ∀ 𝑤  ∈  ( 𝐴  ×  𝐵 ) ( ( 𝐹 ‘ 𝑧 )  =  ( 𝐹 ‘ 𝑤 )  →  𝑧  =  𝑤 ) | 
						
							| 47 |  | dff13 | ⊢ ( 𝐹 : ( 𝐴  ×  𝐵 ) –1-1→ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ↔  ( 𝐹 : ( 𝐴  ×  𝐵 ) ⟶ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ∧  ∀ 𝑧  ∈  ( 𝐴  ×  𝐵 ) ∀ 𝑤  ∈  ( 𝐴  ×  𝐵 ) ( ( 𝐹 ‘ 𝑧 )  =  ( 𝐹 ‘ 𝑤 )  →  𝑧  =  𝑤 ) ) ) | 
						
							| 48 | 6 46 47 | mpbir2an | ⊢ 𝐹 : ( 𝐴  ×  𝐵 ) –1-1→ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) | 
						
							| 49 |  | xpsfrnel | ⊢ ( 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ↔  ( 𝑧  Fn  2o  ∧  ( 𝑧 ‘ ∅ )  ∈  𝐴  ∧  ( 𝑧 ‘ 1o )  ∈  𝐵 ) ) | 
						
							| 50 | 49 | simp2bi | ⊢ ( 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  →  ( 𝑧 ‘ ∅ )  ∈  𝐴 ) | 
						
							| 51 | 49 | simp3bi | ⊢ ( 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  →  ( 𝑧 ‘ 1o )  ∈  𝐵 ) | 
						
							| 52 | 1 | xpsfval | ⊢ ( ( ( 𝑧 ‘ ∅ )  ∈  𝐴  ∧  ( 𝑧 ‘ 1o )  ∈  𝐵 )  →  ( ( 𝑧 ‘ ∅ ) 𝐹 ( 𝑧 ‘ 1o ) )  =  { 〈 ∅ ,  ( 𝑧 ‘ ∅ ) 〉 ,  〈 1o ,  ( 𝑧 ‘ 1o ) 〉 } ) | 
						
							| 53 | 50 51 52 | syl2anc | ⊢ ( 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  →  ( ( 𝑧 ‘ ∅ ) 𝐹 ( 𝑧 ‘ 1o ) )  =  { 〈 ∅ ,  ( 𝑧 ‘ ∅ ) 〉 ,  〈 1o ,  ( 𝑧 ‘ 1o ) 〉 } ) | 
						
							| 54 |  | ixpfn | ⊢ ( 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  →  𝑧  Fn  2o ) | 
						
							| 55 |  | xpsfeq | ⊢ ( 𝑧  Fn  2o  →  { 〈 ∅ ,  ( 𝑧 ‘ ∅ ) 〉 ,  〈 1o ,  ( 𝑧 ‘ 1o ) 〉 }  =  𝑧 ) | 
						
							| 56 | 54 55 | syl | ⊢ ( 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  →  { 〈 ∅ ,  ( 𝑧 ‘ ∅ ) 〉 ,  〈 1o ,  ( 𝑧 ‘ 1o ) 〉 }  =  𝑧 ) | 
						
							| 57 | 53 56 | eqtr2d | ⊢ ( 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  →  𝑧  =  ( ( 𝑧 ‘ ∅ ) 𝐹 ( 𝑧 ‘ 1o ) ) ) | 
						
							| 58 |  | rspceov | ⊢ ( ( ( 𝑧 ‘ ∅ )  ∈  𝐴  ∧  ( 𝑧 ‘ 1o )  ∈  𝐵  ∧  𝑧  =  ( ( 𝑧 ‘ ∅ ) 𝐹 ( 𝑧 ‘ 1o ) ) )  →  ∃ 𝑎  ∈  𝐴 ∃ 𝑏  ∈  𝐵 𝑧  =  ( 𝑎 𝐹 𝑏 ) ) | 
						
							| 59 | 50 51 57 58 | syl3anc | ⊢ ( 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  →  ∃ 𝑎  ∈  𝐴 ∃ 𝑏  ∈  𝐵 𝑧  =  ( 𝑎 𝐹 𝑏 ) ) | 
						
							| 60 | 59 | rgen | ⊢ ∀ 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) ∃ 𝑎  ∈  𝐴 ∃ 𝑏  ∈  𝐵 𝑧  =  ( 𝑎 𝐹 𝑏 ) | 
						
							| 61 |  | foov | ⊢ ( 𝐹 : ( 𝐴  ×  𝐵 ) –onto→ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ↔  ( 𝐹 : ( 𝐴  ×  𝐵 ) ⟶ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ∧  ∀ 𝑧  ∈  X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) ∃ 𝑎  ∈  𝐴 ∃ 𝑏  ∈  𝐵 𝑧  =  ( 𝑎 𝐹 𝑏 ) ) ) | 
						
							| 62 | 6 60 61 | mpbir2an | ⊢ 𝐹 : ( 𝐴  ×  𝐵 ) –onto→ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) | 
						
							| 63 |  | df-f1o | ⊢ ( 𝐹 : ( 𝐴  ×  𝐵 ) –1-1-onto→ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ↔  ( 𝐹 : ( 𝐴  ×  𝐵 ) –1-1→ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 )  ∧  𝐹 : ( 𝐴  ×  𝐵 ) –onto→ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) ) ) | 
						
							| 64 | 48 62 63 | mpbir2an | ⊢ 𝐹 : ( 𝐴  ×  𝐵 ) –1-1-onto→ X 𝑘  ∈  2o if ( 𝑘  =  ∅ ,  𝐴 ,  𝐵 ) |