Bill and Mark, a married couple, manage apartments and they are required to live in the direct vicinity of the apartment as a condition of their employment. Instead of providing an apartment to Bill and Mark rent-free, the apartment owner gives Bill and Mark a housing allowance of $750 each month. Bill and Mark use $500 of the $750 to rent an apartment unit right across the street from the building they manage. What amount, if any must be included in Bill and Marks gross income? Group of answer choices $0 $250 $500 $750