In a 100-unit apartment building, when the price charged per apartment rental is (830 + 30x) dollars, then the number of apartments rented is 100 - x and the total revenue for the building is
R(x) = (830 + 30x) (100 - x)
where x is the number of $30 rent increases (and also the resulting number of unrented apartments). Find the marginal revenue when x = 10. Does this tell you that the rent should be raised (causing more vacancies) or lowered? Explain.