Apply the $Q R$ algorithm to the following non-symmetric matrices to find their eigenvalues to 3 decimal places:
(a) $\left(\begin{array}{rr}-1 & -2 \\ 3 & 4\end{array}\right)$,
(b) $\left(\begin{array}{ll}2 & 3 \\ 1 & 5\end{array}\right)$,
(c) $\left(\begin{array}{rrr}2 & 1 & 0 \\ 2 & 0 & -3 \\ 0 & -2 & 1\end{array}\right)$,
(d) $\left(\begin{array}{rrr}2 & 5 & 1 \\ 2 & -1 & 3 \\ 4 & 5 & 3\end{array}\right)$,
(e) $\left(\begin{array}{rrrr}6 & 1 & 7 & 9 \\ 6 & 8 & 14 & 9 \\ 3 & 1 & 4 & 6 \\ 3 & 2 & 5 & 3\end{array}\right)$