Solve the Standard Minimization Problem Using Duality $c = 6 s + 6 t$

Short Answer

Solve the standard minimization problem using duality.
Minimize $c = 6 s + 6 t$ subject to $\begin{array} { l } s + 4 t \geq 20 \\4 s + t \geq 20 \\s \geq 0 , t \geq 0\end{array}$ ​ $s =$ __________
​ $t =$ __________
​ $c =$ __________