A large hotel is considering giving the following group discount on room rates: the regular price of $120 decreases by $2 for each room rented. For example, one room costs $118, two rooms cost $116 * 2 = $232, three rooms cost $114 * 3 = $342, and so on. 

(a) Write a formula for a function R that gives the revenue for renting x rooms. 

(b) Sketch a graph of R. What is a reasonable domain?

(c) Determine the maximum revenue and the corresponding number of rooms rented.