confusing question? use hierarchical or simultenous

Question

if i use hierarchical system then the equation : 50 = 10 + 0.3(p*400 + (1-p)*125)... is correct?

Comments

50 = 0.7*10 + 0.3(p*(400+125) + (1-p)*125) should be this

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you are using simultenous? because if you are saying this is for hierarchical then i am not convinced, also how to understand this will be hierarchical or simultenous

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also replacing a dirty page includes the page fault time.

Answer 1

Referring https://gateoverflow.in/3500/gate2007-it-58

50 = 0.7*10 + 0.3(p*(400) + (1-p)*125)

p = 0.0667

because 400 is time taken to replace dirty page which includes page fault time