[gilbertocarlos]

Assuming for disadvantages:
6: *2
9: *1.5
12: *1
15: *0.5

We could have
3: 2.5
4: 2.333
5: 2.16667
6: 2
7: 1.83333
8: 1.6667
9: 1.5
10: 1.3333
11: 1.16667
12: 1
13: 0.8333
14: 0.66667
15: 0.5
16: 0.333
17: 0.1667