An owner of an electric bike rental company has determined that if they charge customers Rs xper day to rent a bike, where 50 < x < 200, then number of bikes (n), they rent per day can be shown by linear function n(x) = 2000 - 10x. If they charge Rs. 50 per day or less, they will rent all their bikes. If they charge Rs. 200 or more per day, they will not rent any bike.

Based on the above information, answer the following questions.
Total revenue R as a function of x can be represented as
(a) 2000x - 10x²
(b) 2000x + 10x²
(c) 2000 - 10x
(d) 2000 - 5x²