Q$3$: Can we construct a PRG from a PRF $($assuming the PRF output length is larger than the key length or the input length$)?$ If yes, give the concrete construction and briefly explain; if not, explain why. $(10$ pts$)$

Symmetric key encryption: Suppose $($KeyGen$,$ Enc, Dec$)$ is an IND$-$CPA secure symmetric key encryption. We define the following new encryption algorithms, are the new schemes still IND$-$CPA secure$?$ Briefly explain why. If you believe it is insecure, provide an explicit attacker violating the IND$-$CPA definition.