(a) $\mathbf{A}^{T} \mathbf{A}=\left(\begin{array}{lll}4 & 8 & -10\end{array}\right)\left(\begin{array}{r}4 \\ 8 \\ -10\end{array}\right)=(180)$
(b) $\mathbf{B}^{T} \mathbf{B}=\left(\begin{array}{l}2 \\ 4 \\ 5\end{array}\right)\left(\begin{array}{lll}2 & 4 & 5\end{array}\right)=\left(\begin{array}{rrr}4 & 8 & 10 \\ 8 & 16 & 20 \\ 10 & 20 & 25\end{array}\right)$
(c) $\mathbf{A}+\mathbf{B}^{T}=\left(\begin{array}{r}4 \\ 8 \\ -10\end{array}\right)+\left(\begin{array}{l}2 \\ 4 \\ 5\end{array}\right)=\left(\begin{array}{r}6 \\ 12 \\ -5\end{array}\right)$