Concept:The total output reaches its highest point when the marginal product of the variable input is zero.
Explanation:Marginal product (
MP) is the additional output gained from using one more unit of the variable input.
As long as
MP>0, total output continues to increase.
When
MP falls to exactly zero, the last unit of input adds nothing to total output.
At this point, total output is at its maximum level.
If more input is added beyond this stage,
MP becomes negative and total output starts to fall.
Therefore, maximum total output occurs at the point where
MP=0.
Answer:MP=0 (Option A)