[1, 3, 1] ⨯ [1, 2, 2] = [4, -1, -1]
[1, 2, 1] + r·[1, 3, 1] + s·[4, -1, -1] = [2, -1, 3] + t·[1, 2, 2] --> r = - 5/2 ∧ s = 5/18 ∧ t = - 43/18
5/18·|[4, -1, -1]| = 5/6·√2
[1, 2, 1] - 5/2·[1, 3, 1] = [-1.5, -5.5, -1.5]
[2, -1, 3] - 43/18·[1, 2, 2] = [- 7/18, - 52/9, - 16/9]