P3.4 Demand Function. The Creative Publishing Company (CPC) is a coupon book publisher with markets in several southeastern states. CPC coupon books are sold directly to the public, sold through religious and other charitable organizations, or given away as promotional items. Operating experience during the past year suggests the following demand function for CPC's coupon books where Q is quantity, P is price ($), Pop is population, I is disposable income per household ($), and A is advertising expenditures ($).