Consider the liquid$/$liquid staged extraction problem that we discussed in class.

$A=([-11,10,0,0,0],[1,-11,10,0,0],[0,1,-11,10,0],[0,0,1,-11,10],[0,0,0,1,-11]),b=([-0\mathrm{.}1],[0],[0],[0],[0])$

$($a$)$ Show that the A matrix is not diagonally dominant.