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 375 335

Sales(millions) 968 1,184

(a)

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.