The Figure Below Shows Output of a Firm at Different

The figure below shows output of a firm at different number of workers. Payment to workers is the only variable cost of the firm.

-Refer to the figure above.If the price of the output is $5.00 per unit and the wage is $30 per worker,the firm's optimal choice in the short run is to hire ________ workers.

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