Consider the following page reference string:

1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6.

How many page faults would occur for the following replacement

algorithms, assuming four frames are there?

Remember that all frames are initially empty, so your first unique pages

will cost one fault each.

LRU replacement

FIFO replacement

Optimal replacement [9]