$1.$Consider the page reference string: $0,1,7,2,3,2,7,1,0,3.$ How many page faults will occur for the FIFO page replacement algorithm? Assume that four page frames are used and all four page frames are initially empty.

$2.$ A computer has four page frames, whose the time of loading, time of last access, and the R and M bits are shown below $($the times are in clock ticks$)$:

$($a$)$ Which page will NRU replace?

$($b$)$ Which page will second chance replace?

$\backslash$table$[[$Page$,$Loaded,Last ref.,R$,$M$],[0,126,280,1,0],[1,230,265,0,1],[2,140,270,0,0],[3,110,285,1,1]]$