9. Processor utilization is the percentage of time that the processor spends doing useful work (such as executing arithmetic instructions). Assume that an individual process in a system spends about 65% of its time waiting for I/O operations to be completed (not useful work). When Process X is waiting on I/O, the processor can execute Process Y. For both parts (a) and (b), show your work. (1 point) a. What is the processor utilization if three processes are loaded into memory? b. How many processes should we keep in memory if we want processor utilization to be at least 90%?