4. Show that xy((A(x)B(y))(C(x,y)B(y))) is logically equivalent to xy(B(y)(A(x)C(x,y))). Make sure to cite all steps (e.g. De Morgan's law). You should neither combine steps nor skip steps. The only steps that can be combined on a single line are the associative and commutative laws.(10 points) 5. Rewrite each of these statements so that no negation is to the left of a quantifier. Push all negations in as far as they will go. This means past the conditionals and biconditionals as well.(5 points each) (a) xyz(P(x,y)S(y,z))) (b) yx(R(x,y)zS(z,y))