△XYZ is right-angled at Y. The acute angle at X is 28∘. Side YZ is produced beyond Z to a point W.
a. (i) Find ∠XZY.
b. (ii) Determine the exterior angle ∠XYZW.
c. (iii) Show, by direct calculation, that the value obtained in part (ii) equals the sum of the two interior opposite angles of △XYZ. State those two angles clearly.