Suppose that $A, B, C, D$, and $E$ are the following matrices:
$$
\begin{array}{c}
A=\left[\begin{array}{cc}
3 & 0 \\
-1 & 2 \\
1 & 1
\end{array}\right], B=\left[\begin{array}{cc}
4 & -1 \\
0 & 2
\end{array}\right], C=\left[\begin{array}{ccc}
1 & 4 & 2 \\
3 & 1 & 5
\end{array}\right] \\
D=\left[\begin{array}{ccc}
1 & 5 & 2 \\
-1 & 0 & 1 \\
3 & 2 & 4
\end{array}\right], \text { and } E=\left[\begin{array}{ccc}
6 & 1 & 3 \\
-1 & 1 & 2 \\
4 & 1 & 3
\end{array}\right]
\end{array}
$$
Determine whether the following matrix expressions are defined, and, for those that are defined, compute the resulting matrix.
(a) $D+E$
(b) $D-E(c) 5 A(d)-7 C$
(e) $2 B-C$
$(f) 2 E-2 D(g)-3(D+2 E)$
$(h) A-A$
(i) $A B$
(j) $B A$
$(k)(3 E) D$
$(l)(A B) C(m) A(B C)(n)(4 B) C+2 B$
(o) $D-3 E$
$(p) C A+2 E$
$(q) 4 E-D(r) D D$