21. A given program runs in 8 minutes on one Intel Pentium 4 processor. How long would it take to execute the same program on a multiprocessor system with 4 (four) identical Intel Pentium 4 processors? Explain your answer (Assume that there are no other user processes in the system). 22. Briefly explain the function of the medium-term scheduler. How can it improve the system performance? Explain. 23. The Android operating system defines a hierarchy of importance among the processes. What is the motivation for defining such a hierarchy? How would the system performance be affected if such a hierarchy was not defined