Let A(4, −3), B(2k, 1) and C(−2, 5) be three points in the coordinate plane, where k is a real number.
(a) Find, in terms of k, the lengths AB, BC and AC.
(b) If the three points A, B and C lie on a single straight line with B between A and C, determine all possible values of k.
(c) For each value of k obtained in part (b), write the exact numerical value of AB.