You can put this solution on YOUR website! We have the function R = 36x^(2/3) – 2x
The function is maximized at the point where the derivative is equal to 0.
dR/dx = 0 = (2/3)36x^(-1/3) - 2.
Solving for x we get
12x^(-1/3) = 1 -> x^(1/3) = 12 -> x = 12^3 = 1728
So the answer is 1728 units.
The graph looks like this: