Exercise 4. [20 Marks] Consider a 64-bit computer with a simplified memory hierarchy. This hierarchy contains a single cache and an unbounded backing memory. The cache has the following characteristics: - Direct-Mapped, Write-through, Write allocate. - Cache blocks are 4 words each. - The cache has 256 sets. (a) Consider the following code fragment in the C programming language to be run on the described computer. Assume that: program instructions are not stored in cache, arrays are cache-aligned (the beginning of the array aligns with the beginning of a cache line), ints are 32 bits, and all other variables are stored only in registers. int N=32768 int A[N]; for ( int i=0;i