Question $3.$ Give a condition$($s$)$ on the matrix A that keeps the encryption$/$decryption process well$-$defined.

Question $4.$ Explain why the matrix A given by

$A=\left[\begin{array}{cc}1& -1\\ 1& -1\end{array}\right]$

would make a very poor key. In your explanation, use terms from class.

Question $5.$ You are trying to increase the encryption$/$decryption complexity and want to use a matrix A with three rows and two columns. Would this be an effective strategy?

$3,4,$ and $5$ please