Question

An agro-processing enterprise operates in the short run with a fixed processing plant and variable labor ($L$). When $3$ units of labor are employed, the average product ($AP$) of labor is $21\text{ units}$. Adding a $4\text{th}$ unit of labor yields a marginal product ($MP$) of $25\text{ units}$. When a $5\text{th}$ unit of labor is hired, the average product ($AP$) declines to $21\text{ units}$. Finally, employing a $6\text{th}$ unit of labor results in a total product ($TP$) of $114\text{ units}$. What is the marginal product ($MP$) of the $6\text{th}$ unit of labor?