Find the inverse of the following Matrices: $\begin{array}{lll}3 & 2 & 1\end{array}$ $\begin{array}{lll}1 & 6 & 3\end{array}$ (a) $\boldsymbol{A}=\begin{array}{lll}-1 & 5 & 4\end{array}$ (b) $\boldsymbol{B}=\begin{array}{llll}-4 & -5 & 7\end{array}$ $\begin{array}{lll}5 & 7 & -9\end{array}$ $\begin{array}{lll}8 & 4 & 2\end{array}$ (c) $\boldsymbol{C}=\begin{array}{rrr}-1 & -2 & 5 \\ -4 & 7 & 2 \\ 7 & -8 & -1\end{array}$