how do I get to c) ?

Question 44-45 Fixed costs are (700,000 per year and a variable cost of 670 is incurred for every additional unit produced. The current selling price is 6150 and at this price 10,000 units are demanded per year. It is estimated that for each successive increase (decrease) in price of E2, annual demand would be proportionally reduced (increased) by 500 units. DJ E/0 45. What is the marginal revenue? A) (250-0.002x B) (70-E0.001x C) (190-E0.008x D) (150-60.004x