“…The expected forecast sales volume/total demand, D ( w , p ), for the original product is modeled as a displaced log‐linear function of w and p : where D 1 >0, , d 1 >1, and d 2 >0. The constant d 1 is the rate of decrease of the sales volume with the increasing price of the product, d 2 is the rate of increase of the sales volume with the increasing warranty length, D 1 is a demand amplitude factor, and D 2 is a warranty displacement constant.…”