A store has been selling 200 MP3 players a week at 300$ each. A market survey indicates that for each $10 rebate offered to the buyers, the number of sets sold will increase by 20/week. a) find the demand function and the revenue function. b) How large a rebate should the store offer to maximize its revenue? a) Let n be the # of price increases Let x be the number of MP3 players Let p be the price of 1 MP3 player x= 200 + 20n x-200/20= 20n/20 1) n=x-200/20 2) d= 300-10n sub 1 into 2 d(x)= 300-10(x-200/20) d(x)= 400-x/2 r(x) = xd(x) = 400 - x^2/2 b) after doing these steps...I am not sure what to do from here. Can someone explain how to approach this step? Thank you so much!