(5) In a demand paging system, consider the following page reference string: 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 1, 2, 3, 4, 1, 2, 3, 1, 2, 1. If a process is allocated four frames, how many page faults would occur for the following replacement algorithms: LRU replacement FIFO replacement Optimal replacement