Help please

$($a$)$ Develop a minimum$-$cost schedule for part$-$time employees. $($Let $x_i=$ the number of part$-$time employees who start work beginning at hour $\frac{?}{?}$ where $i=1=11$:$00$ a$.$m$.,i=2=$ Noon, etc$).$

Min$30\mathrm{.}4x_1+30\mathrm{.}4x_2+30\mathrm{.}4x_3+30\mathrm{.}4x_4+30\mathrm{.}4x_5+30\mathrm{.}4x_6+30\mathrm{.}4x_7+30\mathrm{.}4x_8$

s$.$t$.$

$11$:$00$ a$.$m$.$

$6$:$00$ p$.$m$.$

$7$:$00$ p$.$m$.$

$8$:$00$ p$.$m$.$

$9$:$00$ p$.$m$.$

$x_1,x_2,x_3,x_4,x_5,x_6,x_7,x_{8}0$

Find the optimal solution.