Predicate Logic using Quantifiers

Question

$$\lnot \forall y: Y.A\vdash \exists y: Y.(A\rightarrow B)$$

Need to prove that LHS entails RHS, however I'm confused as to how to do it. Never used a negation on a universal quantifier before.

Any help would be appreciated.

Answer 1

HINT $$\lnot \forall y: Y.A \equiv \exists y: \lnot Y.A$$