Ali is a student at the University. He recently purchased a car for OMR5,000 to use it for going to the University. Ali also expects that other friends might ask for transportation from him. He expects a total monthly revenue of OMR50. He expects fuel cost to be OMR30 per month. One of Ali's friends is a taxi driver. He offered Ali to take him to University for a monthly fee of OMR20. Because he does not have to drive, Ali believes that he can perform online work that would earn him a monthly revenue of OMR20. What is the differential revenue in this scenario? Select one: @a, OMR50 b. OMR10 C. OMR20 d. OMR40 e. OMR30