As there are 256 instructions .
256 instructions so 8 bits for instruction (as 2^8=256).
8 flags so 3 bits for flag (2^3=8).
48 control signals so 6 bits for control signals as this is vertical micro programming so decoder will be used so we use 6:64 decoder
so total :- 8+3+6 = 17 bits (so control word is of 17 bits)
Now we have to find total size of memory so :
Each micro instruction have control word of 17 bits .And we have 256 micro instructions :-
So -
(17 x 256 ) / 8 Bytes
544 Bytes