A music store predicts that every dollar increase in the price of any CD will cause sales to decrease by 10 000 units a year. The store now sells 300 000 CD's a year at $15 each.

a)Develop a model that represents the store's sales revenue

b)Using this model, determine when the revenue will increase and decrease

the revenue decreases everywhere

c)What is the rate of change in revenue if price increases by $2?