The points A(2,−1,3), B(5,2,k) and C(8,5,9) lie on the same straight line.
(i) Find the value of k that makes the three points collinear.
(ii) In the above situation, in what ratio does the point B divide the line segment AC?
a. Find the value of k such that A, B and C are collinear.
b. For the value of k obtained, determine the ratio in which B divides AC, clearly stating whether it is internal or external division.