Suppose there are 6 memory blocks B1, B2, B3, B4, B5, and B6 with corresponding sizes of 300 KB, 600 KB, 380KB, 200 KB, 750 KB, and 125 KB. And we have 5 processes, P1, P2, P3, P4, and P5, with corresponding request sizes of 115KB, 500KB, 358KB, 200 KB, and 375 KB. When applying the best-fit algorithm, which memory block is process P5 assigned to?