A box (with no top) is to be constructed from a piece of cardboard of sides $A$ and $B$ by cutting out squares of length $h$ from the corners and folding up the sides as in the figure below:

Suppose that the box height is $h = 3$ in. and that it is constructed using 120 $\text{in.}^2$ of cardboard (i.e., $AB = 120$). Which values $A$ and $B$ maximize the volume?
$A =$ in.
$B =$ in.