A) If you cut off half the peaks (3.5 ft down from the top), they will just fill the valleys making a rectangle 18.5 ft by 30 ft. The area is the product of these dimensions. A = (18.5 ft)*(30 ft) = 555 ft²
b) To determine the number of quarts of paint required, divide this number by 90 ft². Since you cannot buy a partial quart, if there is any remainder, use the next higher integer number of quarts. 555/90 ≈ 6.2 so Pat should buy 7 quarts of paint.
