| Step | Hyp | Ref | Expression | 
						
							| 1 |  | ressbas.r |  |-  R = ( W |`s A ) | 
						
							| 2 |  | ressbas.b |  |-  B = ( Base ` W ) | 
						
							| 3 | 1 2 | ressbas |  |-  ( A e. _V -> ( A i^i B ) = ( Base ` R ) ) | 
						
							| 4 |  | inss2 |  |-  ( A i^i B ) C_ B | 
						
							| 5 | 3 4 | eqsstrrdi |  |-  ( A e. _V -> ( Base ` R ) C_ B ) | 
						
							| 6 |  | reldmress |  |-  Rel dom |`s | 
						
							| 7 | 6 | ovprc2 |  |-  ( -. A e. _V -> ( W |`s A ) = (/) ) | 
						
							| 8 | 1 7 | eqtrid |  |-  ( -. A e. _V -> R = (/) ) | 
						
							| 9 | 8 | fveq2d |  |-  ( -. A e. _V -> ( Base ` R ) = ( Base ` (/) ) ) | 
						
							| 10 |  | base0 |  |-  (/) = ( Base ` (/) ) | 
						
							| 11 |  | 0ss |  |-  (/) C_ B | 
						
							| 12 | 10 11 | eqsstrri |  |-  ( Base ` (/) ) C_ B | 
						
							| 13 | 9 12 | eqsstrdi |  |-  ( -. A e. _V -> ( Base ` R ) C_ B ) | 
						
							| 14 | 5 13 | pm2.61i |  |-  ( Base ` R ) C_ B |