A demand paging system,with page table held in register,takes 5 ms to service a page fault if an empty page is available ,or if the page to be replaced is not dirty.It takes 15 ms if the replaced page is dirty.Memory access time of 2 ms and that the page to be replaced is 60% dirty of the time.What is the approximate maximum acceptable page fault to meet this access time requirement ? If emat is 2 ms