When there is a context switch from one process to another, the OS kernel invokes the function ContextSwitch which saves the context of the currently executing process into its PCB and then inserts the process to an appropriate queue (i.e., ready queue or a blocked queue). It is necessary that ContextSwitch is atomic (i.e., unbreakable: either done or not-done; nothing in between). Explain the following: a) Why must ContextSwitch be atomic? b) Give an example scenario of what can go wrong if ContextSwitch is not atomic. c) How can it be made atomic in practice?