Using ${?}_{c_1}$ and $c_2$ to represent the

objective coefficients of $x_1$ and $x_2,$

respectively, the slope of a line for

the objective function can be

represented by

min,$4x_1+20x_2$

$,$

$s.t.7x_1+2x_{2}14$

$,5x_1+6x_{2}30$

$,2x_1+10x_{2}20$

$x_1,x_{2}0$