Practice Exercise:

EXISTS v(I) FORALL x(I) P(OII) x v AND FORALL x [S(OI) x IMPLIES EXISTS y(I) Q(OII) y x] AND FORALL x FORALL y [P x y IMPLIES ~Q x y] IMPLIES EXISTS u(I) .~S u

All rules and commands 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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