Suppose 20 states increase the minimum wage, while the remaining 30 states do not. Additionally, suppose that employment increases from 260,000 to 300,000 in the 20 states that increased minimum wage and from 230,000 to 330,000 in the remaining 30 states around the time that minimum wage increased. What is the difference-in-difference estimator of the effect of minimum wage on employment? A. 100,000 B. 40,000 C. 60,000 D. -60,000