Determine whether or not the following matrices are convergent:
(a) $\left(\begin{array}{rr}2 & -3 \\ 3 & 2\end{array}\right)$,
(b) $\left(\begin{array}{rr}.6 & -3 \\ .3 & .7\end{array}\right)$,
(c) $\frac{1}{5}\left(\begin{array}{rrr}5 & -3 & -2 \\ 1 & -2 & 1 \\ 1 & -5 & 4\end{array}\right)$,
(d) $\left(\begin{array}{lll}.8 & .3 & .2 \\ .1 & .2 & .6 \\ .1 & .5 & .2\end{array}\right)$.