Here's my attempt
P(6) = P( 2 on first roll) * P ( 4 on second roll) + P(4 on first roll) *P(2 on second roll) =
(1/4)(2/3) + ( 1/2) (1/3) =
2/12 + 1/6 =
4/12 =
1/3
P (8) = P(4 on both rolls) = (1/2) ( 1/3) = 1/6
P(9) = P( 2 on first roll) * P ( 7 on second roll) + P(7 on first roll) *P(2 on second roll) =
(1/4)(1/3) + ( 1/4) (1/3) =
1/12 + 1/12 =
2/12 =
1/6
P(11) = P( 4 on first roll) * P ( 7 on second roll) + P(7 on first roll) *P(4 on second roll) =
(1/2)(1/3) + ( 1/4) (2/3) =
1/6 + 2/12 =
2/12 + 2/12 =
4/12 =
1/3
So...
P(6) = 1/3
P (8 or 9) = 1/6 + 1/6 = 1/3
P(11) = 1/3
So....D seems to provide a fair division
D)If the sum is 6, a small cone will be ordered.
If the sum is 8 or 9, a medium cone will be ordered.
If the sum is 11, a large cone will be ordered.