How many 256times8 ROMs are needed to make a 2048times8 ROM

How many 256times8 ROMs are needed to make a 2048times8 ROM and what kind of decoder should be used? (Only use the 256times8 ROMs) # of 256times8 ROMs: 8, type of decoder: 4times8 # of 256X8 ROMs: 6, type of decoder: 2times8 # of 256X8 ROMs: 4, type of decoder: 3times8 # of 256X8 ROMs: 8, type of decoder: 3times8

Solution

Ans D.

8 256×8 ROMs are required and 3×8 decoder is used