Please help me write a detailed proof of why this scheme is insecure, with proofs of the insecurity. I will rate, thank you!

2. Show that CBC-MAC is insecure for message space M=({0,1}), meaning that the attacker can call the library subroutines with m 's of different lengths and the same key is used to process all of them. Hint: Request a MAC on two single-block messages, then use the result to forge the MAC of a two-block message