Lines p and q are parallel. A transversal r meets them at points M and N respectively. The angle on the exterior of line p at M and to the left of r measures 75∘.
a. (i) Name the angle on line q that forms a corresponding angle pair with the given 75∘ angle.
b. (ii) Calculate the measure of this angle.
c. (iii) Give a brief reason for your calculation based on the relationship between the two angles.