The coordinates of three points are A(-1, -2, 1), B(-3, 4, -5) and C(0, -2, 4).
(i) Find a vector equation of the line AB.
(ii) Find the coordinates of the midpoint M of AB.
(iii) The point N lies on BC.
Given that $2|BN| = |NC|$, find the equation of the line MN.