A store has been selling 200 DVD burners sold per week at 400 each. A market survey indicates that for each $ 20 rebate offered to buyers, the number of units sold will increase by 40 a week. Find the demand function and the revenue function. How large a rebate should the store offer to maximize its revenue

The answer is "50".

Step-by-step explanation:

Let,

If we assume the $20 reduction would raise the number of items sold to $40 so the increment is (x - 200) if x is the number of units sold.

if R'(x)=0

x=300

if  0 < x  < 300  and R(x) > 0 then R(x) for maximum x is = 300

The rebate must be  : 400 - 350  = 50

it would be:

c.parallelogram.

step-by-step explanation: