Page Replacement Policies
Page replacement policies are used in computer systems to decide which pages to remove from main memory when there is a page fault and new pages need to be brought in. Two commonly used page replacement policies are LRU (Least Recently Used) and FIFO (First-In-First-Out).

Virtual Page Reference String
In this question, we are given the virtual page reference string: 1, 2, 3, 2, 4, 1, 3, 2, 4, 1. This string represents the sequence of page references made by a process.

Main Memory Size
The computer system has a main memory size of 3 page frames, which means it can hold 3 pages at a time.

LRU Page Replacement Policy
To determine the number of page faults using the LRU page replacement policy, we simulate the execution of the virtual page reference string and keep track of the currently loaded pages.

1. Initially, all page frames are empty.
2. When the first page reference 1 is made, we bring it into the first page frame. The page fault count is 1.
3. When the second page reference 2 is made, we bring it into the second page frame. The page fault count is 2.
4. When the third page reference 3 is made, we bring it into the third page frame. The page fault count is 3.
5. When the fourth page reference 2 is made, we find that page 2 is already in the second page frame. We update its position to the most recently used position. The page fault count remains 3.
6. When the fifth page reference 4 is made, we replace page 1 in the first page frame with page 4. The page fault count is 4.
7. When the sixth page reference 1 is made, we replace page 3 in the third page frame with page 1. The page fault count is 5.
8. When the seventh page reference 3 is made, we replace page 2 in the second page frame with page 3. The page fault count is 6.
9. When the eighth page reference 2 is made, we find that page 2 is already in the second page frame. We update its position to the most recently used position. The page fault count remains 6.
10. When the ninth page reference 4 is made, we find that page 4 is already in the first page frame. We update its position to the most recently used position. The page fault count remains 6.
11. When the tenth page reference 1 is made, we find that page 1 is already in the third page frame. We update its position to the most recently used position. The page fault count remains 6.

Therefore, the number of page faults under the LRU page replacement policy is 6.

FIFO Page Replacement Policy
To determine the number of page faults using the FIFO page replacement policy, we again simulate the execution of the virtual page reference string and keep track of the currently loaded pages.

1. Initially, all page frames are empty.
2. When the first page reference 1 is made, we bring it into the first page frame. The page fault count is 1.
3. When the second page reference 2 is made, we