i am getting 3.6
@srestha shouldn't the hit rate of l2 be 30/40 and question clearly says heirarchical . so we must add miss penalty to second and third term.
@srestha your formula is incorrect
it should be
L1 access time+L1 miss %*L2 access time+L1 miss %*L2 miss %*memory time
here is is assumed miss penalty of L2=time required to bring the data from MM to L2 to L1 (as it is hierarchical)
=1 clock cycle+0.04*15+0.04*0.25*200
=3.6 clock cycles
PS-miss % of L2 will be 1/4. as L2 will be referred when there is miss in L1 cache. So hit % in L2=30/40
if it were simultaneous access then hit ratio of L2 would have been 990/1000
@sandygate im getting the same too
but 10 misses in L2 out of 1000
then how u got 0.25?