Terry makes and sells necklaces. He has observed over time that when the price is $9 each, he sells an average of 20 per day.

Terry makes and sells necklaces. He has observed over time that when the price is $9 each, he sells an average of 20 per day. If he increases the price, then his average sales fall by 2 per day for each dollar increase. The materials for each necklace cost $6. Express his profit P as a function of x, the number of necklaces sold.