-City-Mart Is the Only Employer of Sales Clerks in Panburg

-City-Mart is the only employer of sales clerks in Panburg. In the figure above S is the labor supply curve faced by City-Mart, VMP is City-Mart's value of marginal product curve, and MCL is its marginal cost of labor curve. The lowest wage rate at which City-Mart can hire 40 hours of labor per day is

A) $8 per hour.
B) $12 per hour.
C) $4 per hour.
D) $9 per hour.