I think it is 2*7*3!*3!
If we take the arrangement: bgbgbg_
there are 7 choices for "_"
Also if we take gbgbgb_, there are 7 choices for the "_"
And for each of the two cases above, there are 3!*3! arrangements for boys and girs
Total choices = 2*7*3!*3!
"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."
- Bernard Edmonds