Suppose that in addition to repairing your car, you can also spend money advertising. If you repair your car for H hours and buy A column inches of ads in the local paper, your benefit (the amount you receive when you sell your car) is B(H, A) = 400H -10H2 + 200A2+ 10AH, where H and A are finely divisible. What is your marginal benefit of repair work when H = 5 and A = 4? What is your marginal benefit of advertising at that choice? How does an increase in advertising affect the marginal benefit of repair work? Can you think of a reason that might be true?