Suppose a byte-addressable computer using set-associative cache has 2 ²¹ bytes of main memory and a cache of 64 blocks, where each cache block contains 4 bytes

a) If this cache is 2-way set associative, what is the format of a memory address as seen by the cache; that is, what are the sizes of the tag, set, and offset fields? 

b) If this cache is 4-way set associative, what is the format of a memory address as seen by the cache?