Suppose a computer using direct mapped cache has 2^36 words of main memory and a cache of 256 blocks, where each cache block contains 128 words. a. How many blocks of main memory are there? b. What is the format of a memory address as seen by the cache, that is, what are the sizes of the tag, block, and word fields? c. To which cache block will the memory reference 0000063FA_16 map