At: surj is inj gen111121111 1. A: Type 2. B: Type 3. f: AB 4. f1: AB 5. g: BA 6. InvFuns(A; B; f1; g) 7. n: 8. f2: nB 9. g1: Bn 10. InvFuns(n; B; f2; g1) 11. Surj(A; B; f) 12. a1: A 13. a2: A 14. f(a1) = f(a2) 15. (g1 o f o g o f2)(g1(f1(a1))) = (g1 o f o g o f2)(g1(f1(a2))) g1(f1(a1)) = g1(f1(a2))