Find all fixed points for the iterative systems with the following coefficient matrices:
(a) $\left(\begin{array}{ll}7 & .3 \\ .2 & .8\end{array}\right)$,
(b) $\left(\begin{array}{rr}.6 & 1.0 \\ .3 & -.7\end{array}\right)$,
(c) $\left(\begin{array}{rrr}-1 & -1 & -4 \\ -2 & 0 & -4 \\ 1 & -1 & 0\end{array}\right)$,
(d) $\left(\begin{array}{rrr}2 & 1 & -1 \\ 2 & 3 & -2 \\ -1 & -1 & 2\end{array}\right)$.