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At:
delete fenum value is fenum gen12111 1. P : Prop
2. Q : Prop
3. f : {u:| P(u) }{v:| Q(v) }
4. Inj({u:| P(u) }; {v:| Q(v) }; f)
5. Surj({u:| P(u) }; {v:| Q(v) }; f)
6. m : {u:| P(u) }
7. k : {v:| Q(v) }
8. (Replace value k by f(m) in f) {u:| P(u) & u = m }{v:| Q(v) & v = k }
9. b : {v:| Q(v) & v = k }
10. a : {u:| P(u) }
11. f(a) = b 12. c : {u:| P(u) }
13. f(c) = k 14. a = m a:{u:| P(u) & u = m }. (Replace value k by f(m) in f)(a) = b