There are Two Write Hit policies: Write Through  and Write back    There are Two Write miss policies: Write Allocate and No WriteAllocate    There are two memory access techniques: simultaneous andhierarchical access   Can any gentleman PLEASE write formulas for different combinations ?I am having very important competitive exam that can change my life, and i am struggling with these methods badly.For instance one may consider following example and please show me relevant modification of this example.Question : 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 isa) 14.62nsb) 348.47nsc) 29.62nsd) 296.2nsPS:- I know meaning or working of all techniques but don't know how can i drive formulas.Please do it, i really need that badly. It would be GREAT help.Thnks in advance. 
Write through and write back cache policies
computer architecture;memory management;cpu cache