a. Explain the three common reasons why transfer-of-control operations are required in systems control instructions. (6 marks) b. In this example, there is a main program starting at location 4000. This program includes a call to procedure PROC1, starting at location 4500. When this call instruction is encountered, the processor suspends execution of the main program and begins execution of PROCI by fetching the next instruction from location 4500. Within PROC1, there are two calls to PROC2 at location 4800. In each case, the execution of PROCI is suspended and PROC2 is executed. The RETURN statement causes the processor to go back to the calling program and continue execution at the instruction after the corresponding CALL instruction. Use this example to describe how stacks are used to implement nested procedure calls. (6 marks) c. With the aid of an example, explain any three type of instruction. (3 marks)