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243: 3 notch-heptacubes, 3 pinwheel-heptacubes, 3 shelf-heptacubes
2 solutions for B and 2 solutions for C

  3×   3×

empty cube at B
(1 of 2)

empty cube at B
(2 of 2)

empty cube at C
(1 of 2)

empty cube at C
(2 of 2)