Show Stoppers is a monopoly provider of ticket services for the concerts and sporting events and their current service charge is $10.00 . In order to attract one more customer, they have to lower their service charge to $9.50 . Show Stoppers' marginal revenue of this additional customer is:
a. $9.50
b. greater than $9.50.c. less than $9.50.d. between $10.00 and $9.50.