The memory unit of a computer has $256$ K words of $32$ bits each. The computer has an instruction format with four fields: an operation code field, a mode field (to specify one of seven addressing modes), a register address field (to specify one of $60$ processor registers), and a memory address.
What are the number of bits, in each of the below given fields, when the instruction is $one$ memory word long?
- Op-code
- Mode
- Register address
- Memory address
- $6,5,3,18$
- $5,6,3,18$
- $5,18,6,3$
- $5,3,6,18$