Find the distance between parallel lines `bar(r) = (2hat(i) - hat(j) + hat(k)) + lambda (2hat(i) + hat(j) - 2hat(k))` and `bar(r) = (hat(i) - hat(j) + 2hat(k)) + mu (2hat(i) + hat(j) - 2hat(k))`

Answer

`(sqrt(2))/(3)` unit