Consider the following page reference string:
$7, 2, 3, 1, 2, 5, 3, 4, 6, 7, 7, 1, 0, 5, 4, 6, 2, 3, 0 , 1.$
Assuming demand paging with three frames, how many page faults would occur for the following replacement algorithms ?
$•$ $LRU$ $replacement$
$•$ $FIFO$ $replacement$
$•$ $Optimal$ $replacement$