DO BOTH QUESTION!!!!!

$2.$ A rectangular box with open top has a square base whose side is $x$ inches long, and the height of the box is $y$ inches. $($See figure below$)$

$($a$)$ Find the surface area of the box in terms of $x$ and $y,$ that is$,$ the sum of the areas of the $4$ side rectangles plus the area of the square base.

$S=xy+xy+{?}^4+xy+x^2$

$y=4xy+x^2$

$($b$)$ Suppose the volume of the box is fixed at $4$ inches ${?}^3,$ find the values of $x$ and $y$ that minimize the surface area of the box in part $($a$).$ Justify why $x$ and $y$ values you found minimize the surface area.