Answer:
Step-by-step explanation:
The formula for determining the surface area of a cuboid or box is expressed as
Surface area = 2lw + 2lh + 2wh
Where l, w and h represents length, width and height of the box respectively.
2lw represents the area of the top and the bottom of the box. Since she doesn't want to cover the bottom, it becomes lw. Therefore,
Surface area = 15 + 6 + 6 + 10 + 10 = 47 in².
The cost would be
0.25 × 47 = $11.75
Therefore,
Yes, she should have only added the area of five of the six faces.
