The following table shows worldwide sales of a certain type of cell phone and their average selling prices in 2012 and 2013.

Year 2012 2013

Selling Price 385 (in 2012) 315 (in 2013)

Sales (millions) 740 (in 2012) 1,146 in 2013)

Use the data to obtain a linear demand function for this type of cell phone. (Letpbe the price, and letqbe the demand).

q(p) =

Use your demand equation to predict sales if the price is lowered to $255.

million phones

(b)

Fill in the blank.

For every $1 increase in price, sales of this type of cell phone decrease by million units.