Mueller has been approached about providing a new service to its clients. The company will bill clients $140 per hour; the related hourly variable and fixed operating costs will be $75 and $18, respectively. If all employees are currently working at full capacity on other client matters, the per-hour opportunity cost of being unable to provide this new service is: Select one: a. $0. O b. $47. c. $65. O d. $93. e. $140