Considering 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

Find the total number of page faults in each page replacement algorithm given below. Assume that initially the memory is empty. And use the memory with 5 frames.

1) LRU Page Replacement

2) FIFO Page Replacement

3) Optimal Page Replacement