80-c ,because a miss is related to cache line.Initially all lines are empty so 32.Then 2500(50×50,size of array)-2048(32×64,size of cache)=452.this requires 7.0625 cachelines so another 8 misses then 2nd time 8 and 8 =16 .net = 56.
81-c , everytime this first 8 line 0-7 are being replaced and a total of 3 times they've been replaced.