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In a certain system the main memory access time is 100 ns. The cache is 10 time faster than the main memory and uses the write though protocol. If the hit ratio for read request is 0.92 and 85% of the memory requests generated by the CPU are for read, the remaining being for write; then the average time consideration both read and write requests is

a) 28.95ns

b) 348.47ns

c) 29.62ns

d) 296.2ns
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cache =10ns  main memory =100ns

TavgR = 10 + 0.08 * 100

          =10 + 8 

          = 18 ns

TavgW = max(cache,main memory) =100ns since writh though protocol 

Tavg= 0.15 * 100 + 0.85 * 18 =30.3ns

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