Write the sequence of control steps required for the single bus organization in each of the following instructions: a) Add the immediate number NUM to register R1. b) Add the contents of memory-location NUM to register R1. c) Add the contents of the memory-location whose address is at memory-location NUM to register R1. Assume that each instruction consists of two words. The first word specifies the operation and the addressing mode, and the second word contains the number NUM