It takes 15*20*2+ 1*20=620 square centimeters to package a book.
40 copies * 620 = 24800 square centimeters.
Packaging 40 such books requires at least 24,800 square centimeters of wrapping paper.
320*620= 198400 cm2
The surface area of the wrapping paper should be at least 198400 cm2.