The Solo Coal Mine Is the Only Employer in the Small

The Solo Coal Mine is the only employer in the small town of Way out there. The market supply of coal miners is , where W is the annual wage of a coal miner and Q is the number of people who would accept employment as a coal miner. What is the coal mine's marginal expenditure when it hires 100 coal miners?

A) $15,000
B) $20,000
C) $10,000
D) $1,000,000