Solve the Standard Minimization Problem Using Duality $c = 4 s + 7 t + 9 u$

Multiple Choice

Solve the standard minimization problem using duality.
Minimize $c = 4 s + 7 t + 9 u$
Subject to $\begin{array} { l } s + 2 t + 2 u \geq 60 \\2 s + t + 3 u \geq 60 \\s \geq 0 , t \geq 0 , u \geq 0\end{array}$

A) $c = 140$ , $s = 0$ , $t = 20$ , $u = 0$
B) $c = 80$ , $s = 20$ , $t = 0$ , $u = 0$
C) $c = 220$ , $s = 20$ , $t = 20$ , $u = 0$
D) $c = 260$ , $s = 20$ , $t = 0$ , $u = 20$
E) $c = 320$ , $s = 0$ , $t = 20$ , $u = 20$