2) A firm demand describes the quantity of its product that can be sold at various prices, other things being equal. Over period of a year, a tire company varied the prices of a radial tire to estimate its demand. The data are listed below: Price Sales (Demand) ($) ($Million) 20 50 30 40 40 30 40 30 50 30 a) Calculate a line to approximate the firm's demand b) Interpret the meaning of slope