Explain why a quadratic function is a reasonable model for revenue. choose the correct answer below.

Revenue = Sales Volume (x) times Price. Price depends on volume sold: the more you are willing to sell per week, the lower your average price will have to be to get them all sold. 

eg, if there are a fixed number of buyers with a variety of incomes, then you might be able to sell the first 10 per month for £30 each through the up-market High Street jeweller. If you want to sell an extra 10 per month you might have to reduce the price to £15 and sell them through Asda/WalMart. And to move another 10 per month you may have to sell them from a street stall at £5 each!