Answer: a) 2(6!)(4!)
Explanation:
The number of ways the boys can be arranged is: 6!
The number of ways the girls can be arranged is: 4!
The number of ways the groups (boys & girls) can be arranged is: 2
Girls could be in the front .. or in the back ... of the line.
Put these together to get: 6! × 4! × 2