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 ($) 375 315 Sales (millions) 788 1,136 (a) Use the data to obtain a linear demand function for this type of cell phone. (Let p be the price, and let q be 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