A sports store sells about 50 mountainbikes per month at a price of $220 each. For each $20 decrease in price, about 10 more bikes per month are sold.

Write a quadratic function in standard form that models the revenue from bike sales.

50 bikes sold for $220 each yields a revenue of $11000

If you decrease by $20, the amount of sales becomes 60. And the new revenue becomes (200 x 60) = $12000

So, the revenue at any time is given by:

Revenue = (220 - 20x)(50 +10x)

Where x is the number of $20 reduction in price.