Two points in space are A(k,1,2) and B(3,k,0), where k is a real parameter.
a. (i) Find all real values of k for which the distances of A and B from the origin are equal.
b. (ii) For each value of k obtained in part (i), calculate the common distance and state whether it is less than 4, equal to 4, or greater than 4.
c. (iii) Verify that, for the values of k found, the two points A and B lie on the same sphere centred at the origin and determine the radius of this sphere.