Indicate whether each of the following statements is true, false, or uncertain, and explain why:

a. Aproportional tax on all commodities including leisure is equivalent to a lump sum tax.

b. Efficiency is maximized when all commodities are taxed at the same rate.

c. Average cost pricing for a natural monopoly allows the enterprise to break even, but the outcome is inefficient.

d. Toms workplace provides free access to a fitness room; Jerrys does not. Horizontal equity requires that Tom be taxed on the value of having access to the fitness room.