The quadratic function q(x)=x2−4x+m depends on the real parameter m.
a. (i) Find the minimum value of q(x) in terms of m.
b. (ii) Determine the set of all real values of m for which this minimum value is less than or equal to zero.
c. (iii) For each value of m obtained in part (ii), state the coordinates of the point at which q(x) attains its minimum.