its all about two level memory access. Here firsty cpu will check in cache memory if miss occurs then it will go to main memory
but this is not mentioned here ,so we use simultaneous access of cache and main memory so,
110 = h*100 + (1-h)*500
h=97.5%
hence answer is close to (c)
we should not use 600 for cache miss until it is mentioned. I am using hierarchical access(look aside cache).