Exercise:

EXISTS j(B(OB)) FORALL p(OB) [EXISTS x(B) p x IMPLIES p .j p] IMPLIES .FORALL x(A) EXISTS y(B) r(OBA) x y EQUIV EXISTS f(BA) FORALL x r x .f x

All rules and commands, including ADVICE, are allowed.

Only book theorems may be ASSERTed as lemmas without proof.

For a complete list of book theorems, type PROBLEMS.

No more help available. Sorry.

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