| Step | Hyp | Ref | Expression | 
						
							| 1 |  | upgr1e.v |  | 
						
							| 2 |  | upgr1e.a |  | 
						
							| 3 |  | upgr1e.b |  | 
						
							| 4 |  | upgr1e.c |  | 
						
							| 5 |  | upgr1e.e |  | 
						
							| 6 |  | prex |  | 
						
							| 7 | 6 | snid |  | 
						
							| 8 | 7 | a1i |  | 
						
							| 9 | 2 8 | fsnd |  | 
						
							| 10 | 3 4 | prssd |  | 
						
							| 11 | 10 1 | sseqtrdi |  | 
						
							| 12 | 6 | elpw |  | 
						
							| 13 | 11 12 | sylibr |  | 
						
							| 14 | 13 3 | upgr1elem |  | 
						
							| 15 | 9 14 | fssd |  | 
						
							| 16 | 15 | ffdmd |  | 
						
							| 17 | 5 | dmeqd |  | 
						
							| 18 | 5 17 | feq12d |  | 
						
							| 19 | 16 18 | mpbird |  | 
						
							| 20 | 1 | 1vgrex |  | 
						
							| 21 |  | eqid |  | 
						
							| 22 |  | eqid |  | 
						
							| 23 | 21 22 | isupgr |  | 
						
							| 24 | 3 20 23 | 3syl |  | 
						
							| 25 | 19 24 | mpbird |  |