Q$4$: Enc$\_1($k$,$m$)$ is defined as follows:

$-$It runs Enc$($k$,$m$)$ and obtains c$\_0$;

$-$ It runs Enc$($k$,$m$)$ again to obtain c$\_1.$ The final ciphertext will be $($c$\_0,$c$\_1).(10$ pts$)$

Q$5$: Enc$\_2($k$,$m$)$ is defined as follows:

$-$It runs Enc$($k$,$m$)$ and obtains c$\_0$;

$-$It runs f on m to obtain c$\_1,$ where f is a pseudorandom generator. The final ciphertext will be $($c$\_0,$c$\_1).(10$ pts$)$