Write out explicitly the linear program corresponding to finding the shortest path from node $s$

to node $y$ in Figure $24\mathrm{.}2($a$).$

$minimiz{e}_{},d_y$ subject $to$

$d_t{d}_s+3$

$d_x{d}_t+6$

$d_y{d}_s+5$

$d_y{d}_t+2$

$d_z{d}_x+2$

$d_t{d}_y+1$

$d_x{d}_y+4$

$d_z{d}_y+1$

$d_s{d}_z+1$

$d_x{d}_z+7$

$d_2=0.$