From point P on the bank of a wide river, the angle of elevation of the top of a transmission mast on the opposite bank is 25°. From point Q, which lies 200 m closer to the mast along the same straight line as P, the angle of elevation is 35°. Assuming the foot of the mast, P, and Q are collinear and on the same horizontal level,
a. (i) calculate the height of the mast, correct to the nearest metre.
b. (ii) find the horizontal distance of point Q from the foot of the mast.
c. (iii) determine, correct to the nearest degree, the angle of depression of point Q as observed from the top of the mast.