Cason is the manager of a motel. As a condition of his employment, Cason is required to live in a room on the premises so that he would be there in case of emergencies. Cason considered this a fringe benefit since he would otherwise be required to pay $$800$ per month rent. The room that Cason occupied normally rented for $$70$ per night, or $$2,100$ per month. On the average, $90\%$ of the motel rooms were occupied. As a result of this rent$-$free use of a room, what amount is Cason required to include in gross income?

a$.$

$$-0-.$

b$.$

$$800$ per month.

c$.$

$$2,100$ per month.

d$.$

$$1,890($$$2,1000\mathrm{.}90)$