(i) Treat the 6 boys as a single unit or 'block'. This block can be arranged in the line with the 4 girls in (5 + 1)! = 6! ext{ ways.} Within the block, the 6 boys can be arranged among themselves in 6! ways. Thus, the total number of arrangements is 6! \times 5! = 86400.

(ii) To ensure no two girls stand next to each other, arrange the 6 boys first, which can be done in 6! ways. This creates 7 possible spaces (before, between, and after the boys) to place the 4 girls. Choose 4 out of these 7 spaces to place the girls, which can be done in \binom{7}{4} ways. Arrange the 4 girls in these spaces in 4! ways. Thus, the total number of arrangements is 6! \times \binom{7}{4} \times 4! = 604800.