A clothing business finds there is a linear relationship between the number of shirts, Q ,it can sell and the price, P , it can charge per shirt. In particular, historical data shows that 4000 shirts can be sold at a price of $ 133 , while 27000 shirts can be sold at a price of $ 41 . Give a linear equation in the form P = a Q + b that gives the price P they can charge for Q shirts. (This is called a demand function.)