Answer : 3
Let's Assume there are 100 instructions,
so we have 100 fetches for 100 instructions, this will come from instruction cache.
25% that is 25 instructions are Data fetch / store instructions - come from data cache
so in total 100 fetches we will have 2% ie, 2 misses - 200 cycles penality.
from the data stream, 8% ie, 2 misses - 200 cycles penality.
Total cycles taken to execute 100 instructions is 100*2 + 200 + 200 = 600 cycles
CPI = 600/100 = 6.
In a perfect caching solution we have 0 misses and hence the CPI will be default ie, 2 CPI.
Speedup achieved = 6/2 = 3