A baseball team plays in a stadium that holds 48000 spectators. With the ticket price at $8 the average attendance has been 19000. When the price dropped to $4, the average attendance rose to 24000. Find a demand function D ( q ) , where q is the quantity/number of the spectators. (Assume D ( q ) is linear) D ( q ) = (For best results, keep answers in fraction form, not decimals)