Suppose that the revenue in dollars from the sale of x campers is given by R(x) = 60,000x + 40,000(10 + x)-1 - 6000. (a) Find the marginal revenue when 10 units are sold. $ (b) How is revenue changing when 10 units are sold? O The revenue is decreasing. O There is no change in the revenue. O The revenue is increasing.