$(10$ points$)$ Suppose $E_1$ and $E_2$ are encryption procedures of two substitution ciphers and $E_3$ be a permutation.

a$.$ Let $E$ be a new encryption procedure that defined by first applying $E_1$ then $E_2,$ is $E$ more secure than $E_1$ and $E_2?$ Why?

b$.$ Let $E$ be a new encryption procedure that defined by first applying $E_1$ then $E_3,$ is $E$ more secure than $E_1$ and $E_3?$ Why?