Compute each matrix sum or product if it is defined. If an expression is undefined, explain why. Let $A=\left[\begin{array}{ccc}1& 0& -2\\ 4& -5& 3\end{array}\right],B=\left[\begin{array}{ccc}6& -4& 2\\ 1& -4& -2\end{array}\right],C=\left[\begin{array}{cc}1& 2\\ -2& 1\end{array}\right],$ and $D=\left[\begin{array}{cc}3& 5\\ -2& 4\end{array}\right].$

$-3A,B-3A,AC,CD$

Compute the matrix product $-3$A$.$ Select the correct choice below and, if necessary, fill in the answer box within your choice.

$-3A=($Simplify your answer.$)$

B$.$ The expression $-3A$ is undefined because $A$ is not a square matrix.

C$.$ The expression $-3A$ is undefined because matrices cannot have negative coefficients.

D$.$ The expression $-3A$ is undefined because matrices cannot be multiplied by numbers.

Compute the martrix sum B $-3$A$.$ Select the correct choice below and, if necessary, fill in the answer box within your choice.

A$.B-3A=$

$($Simplify your answer.$)$

B$.$ The expression $B-3A$ is undefined because $B$ and $-3$A have different sizes.

C$.$ The expression $B-3A$ is undefined because $A$ is not a square matrix.

D$.$ The expression $B-3A$ is undefined because $B$ and A have different sizes.

Compute the matrix product AC$.$ Select the correct choice below and, if necessary, fill in the answer box within your choice.

$AC=($Simplify your answer.$)$