The Following Table Shows the Total Number of Pizzas Produced

Multiple Choice

The following table shows the total number of pizzas produced by 7 workers.
Table 16-1 $$\begin{array} { | c | c | } \hline \begin{array} { c } \text { Number of } \\\text { workers }\end{array} & \begin{array} { c } \text { Total number of pizzas } \\\text { produced per day }\end{array} \\\hline 0 & 0 \\\hline 1 & 6 \\\hline 2 & 13 \\\hline 3 & 18 \\\hline 4 & 21 \\\hline 5 & 23 \\\hline 6 & 22 \\\hline 7 & 20 \\\hline\end{array}$$
-Refer to Table 16-1.If the pizza industry is competitive and the price of a pizza is $10,then which of the following is true?

A) The marginal value product of the third worker is $50.
B) The marginal value product of the fifth worker is $10.
C) The marginal product of the fourth worker is 21 pizzas.
D) The marginal product of the second worker is 6 pizzas.