The top (Q) of a chimney was sighted from two stations P and R at very different levels, the stations P and R being in line with the top of the chimney. The angle of elevation from P to the top of the chimney was 36°12’ and that from R to the top of the chimney was 16°48’. The angle of elevation from R to a vane 1 m above the foot of the staff held at P was 8°24’. The heights of instruments at P and R were 1.65 m and 1.85 m respectively. The horizontal distance between P and R was 100 m and the R.L. of R was 248.260 m. Find the R.L. of the top of the chimney.