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

Short Answer

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