Suppose Alice and Bob achieve some agreement and want to make it official, thus Alice write down the agreement as a file m and encrypts m using Bobs public key pk to get c. Alice sends c to Bob, trying to convince B that c is the commitment of Alice about the agreement. Would this method work? Explain why.

If Alice further uses a message authentication code, and generate a tag ? on c (using a shared key k). Now Alice sends both c and ? to Bob. Can Bob now be convinced that Alice already committed to the agreement? Explain why.