$3.$ Consider the logic block diagram for a $64$ KB $($kilo$-$byte$)$ RAM below. Note that the Chip Select $($CS$)$ signal is active high for this chip.

a$.$ Show how you would double the data width to $16$ bits while keeping the address range the same.

b$.$ Show how you would expand the memory to a $256$ KB memory by adding multiple instances of this block and a suitable decoder plus logic. Give the address range for each added block.