The Figures Below Give the Production Schedule and the Product

The figures below give the production schedule and the product demand schedule for a firm, which has to decide how many workers to hire. $\begin{array}{c}\begin{array}{lll}\\\text {Workers}\\\text {hired}\\0\\1\\2\\3\\4\\5\\6\end{array}\begin{array}{lll}\text {Total}\\\text {Physical}\\\text {Product}\\0\\10\\18\\25\\30\\34\\37\end{array}\begin{array}{lll}\text {Price of}\\\text {output}\\\$10\\\$10\\\$10\\\$10\\\$10\\\$10\\\$10\\\end{array}\end{array}$
-If the wage = $40 for the time period in question, then the number of workers hired is:

A) 2
B) 3
C) 6
D) 5
E) 4