Answer:
396 square inches
Step-by-step explanation:
First we must find the overall surface area of the cake, which will the total area of all of the faces.
The cake is a rectangular prism, meaning the faces are all rectangles and opposite faces will be identical.
As opposite faces are identical, the area of only 3 faces need to be found, and a formula can be crafted:
, where l is length, w is width, and h is height.
For demonstration purposes, the length will be 12 and the width will be 15.
Substituting, we get:
Now, we must subtract the area that is not covered by frosting. As there is only a lack of frosting on the base, we subtract the area of the base.