$2.$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$],[0,126,280,1,0],[1,230,265,0,1],[2,140,270,0,0],[3,110,285,1,1]]$