Use the following information to answer questions 20-22.

A contractor is building a garage onto the end of a house. The house consists of a triangular prism resting on top of a rectangular prism, as shown in the figure below, The roof of the house is formed by 2 congruent rectangles that are joined at the ridge. The house and the garage are geometrically similar, with each dimension of the garage the corresponding dimension of the house. Some of the lengths of the house, in feet, are as follows:

The contractor will use shingles that cost ＄21 per bundle to cover the roof of the garage. Each 1-gallon can of paint used to paint the inside walls and ceiling of the garage covers exactly 400 square feet with 1 coat of paint.