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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 ...

This result is proven in the following research papers: Johan Hastad, Mats Naslund. The Security of all RSA and Discrete Log Bits. Journal of the ACM, Oct 2003, pp.1--45. W. Alexi, B. Chor, O. Goldrech, C. Schnorr. RSA and Rabin functions: Certain parts are as hard as the whole. SIAM Journal on Computing, vol 17 no 2, pp.194--209. They show that if ...

It's hard to be sure without seeing a bit more context, but the paragraph you quoted looks like it's part of a definition of IND-CPA security (ciphertext indistinguishability under a chosen-plaintext attack) for public-key ciphers. Here's the corresponding definition from the Wikipedia article I linked to above: "For a probabilistic asymmetric key ...