1 x 3 x 11 (6)
In the 1x3x11 there is a solution using the 1x3x4 and the 1x3x7.
1 x 3 x 12 (1)
1 x 3 x 15 (20)
This 1x3x15 uses a 1x3x8 and a 1x3x7. There are other solutions that use a 1x3x4 and a 1x3x11 as well as a 1x3x10 and a 1x3x5. Can you find them?