A computer has the following memory and cache characteristics: $-1$ GB main memory $-256$ KB cache $-$ The cache is $4-$way set associative $-$ There are $16$ words in a block $-$ Each word is $4$ bytes Answer the following questions. Show all calculations. a$.$ How many bits are there in a main memory address? b$.$ How many blocks are there in the main memory? c$.$ How many sets are there in the cache? d$.$ Show the tag, set and word fields of the memory addresses. How many bits are there in each field?