7. Grease Can Harry's Used Car Lot sells an average of 20 used cars each week at a price of $4800 each. The sales department wants to increase the price, but the marketing department predicts that for every $300 increase, sales will fall by one car. A linear function that represents the number of used cars sold in a given week is n(x) = 20 - x, in which x is the number of $300 price increases. A linear function that represents the price per used car is p(x) = 4800 + 300x, in which x is the number of $300 price increases. The revenue generated is calculated by the product of the number of cars sold and the sale price. Find the function s(x), the combination of the two functions that represents the revenue generated for a week. (2 marks)