in a single-user environment, one disk scheduling algorithm might be preferred as its economical while another might be useful in a multi-user environment. Which makes sense for single-user environment and which for multi-user environment? Select one: O a. FCFS in single-user and FCFS in mutli-user O b. FCFS in single-user and LOOK in multi-user c. LOOK in single-user and FCFS in multi-user d. LOOK in single-user and LOOK in multi-user