Operating Systems - Old Questions

3.  Consider the following page reference string : 1, 2, 3, 4, 2, 1, 5, 6, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6. How many page fault would occur for the LRU replacement, FIFO replacement and optimal replacement algorithms. Assuming three, five or seven frames? Remember all frames are initially empty, so your first unique pages will all cost one fault each.