A cache memory needs an access time of 30 ns and main memory 150 ns, what is the average access time of CPU (assume hit ratio = 80%)?

A cache memory needs an access time of 30 ns and main memory 150 ns, w

1.	A cache memory needs an access time of 30 ns and main memory 150 ns, what is the average access time of CPU (assume hit ratio = 80%)?
A.	60 ns
B.	30 ns
C.	150 ns
D.	70 ns
Answer» B. 30 ns