Initially 1 to 20 will be present (20 page fault)
now 20 will be replaced till end of first scan so at end of first scan we will have
1,2,3...19,100. (80 miss)
now 1 to 19 will be hit and for 20 we will replace 1 and so one
note that 100 will not be replaced as we are using optimal
so from 20 till 99 page fault and for 100 page hit
Total fault : 100+80=180
Total Hit: 20 (for 1,2,..19,100)