Why is an Encrypt-and-MAC scheme with deterministic MAC not IND-CPA secure?
I'm a little bit confused by your notation (what's $1^n$ supposed to mean? based on context, it looks like a key or a passphrase, but I've never seen that notation before), but the exercise itself seems to just amount to proving that an Encrypt-and-MAC scheme, using a deterministic MAC of the plaintext which is sent in plain, cannot be IND-CPA secure.

To prove that, keep in mind that there's nothing in the IND-CPA definition saying that the adversary cannot use the encryption oracle on the challenge messages.  Since the MAC is deterministic and sent in plain, the adversary can just compare the MAC parts of two encrypted messages to determine (with very high probability) whether they encode the same plaintext.