In economics, the marginal cost of production is the change in total production cost that comes from making or producing one additional unit. A book publisher found that the cost to produce 1000 calculus textbooks is $25,100, while the cost to produce 2000 calculus textbooks is $50,700. Assume that the cost C(x) is a linear function of x, the number of textbooks produced. What is the marginal cost of a calculus textbook?