How much of the following payments for factor services is likely to be economic rent?
a. The $750 per month that a landlord receives for an apartment rented to students
b. The salary of the Canadian prime minister
c. The annual income of Tiger Woods or Shania Twain
d. The salary of a window cleaner who says, "It's dangerous work, but it beats driving a truck."
e. An engineer at Google headquarters who loves going to work every day