Attempt:

(a)Let be an interpetation, and let be an I-assignment.

Suppose that . We want . And we know that iff there is some with . But how do we show that we have such a d?

(b)Suppose , I have to show that . But I'm confused because assuming means there is some d in the domain with . What could I do? Are there better ways to show that the implication doesn't hold?