Answer
$A = 0.5w^3$
Work Step by Step
Area of a box is length x width x height $A= lwh$)
In the problem, it is given that the base is a squre, so length = width, thus $l = w$
Height is half the width, so $h = 0.5w$
$A = lwh$
$A = (w)w(0.5w)$
$A = 0.5w^3$