Computer · Surveying

A tacheometer was set up at station A and observations were taken on a staff held vertically at B, with the vertical circle reading being zero. The staff intercept readings were 2.980 m, 2.660 m, and 2.340 m. The instrument's multiplying and additive constants were 100 and 0.5, respectively. The backsight reading from A to a staff held at a BM of elevation 1020.50 m was 2.85 m. Find the horizontal distance AB and the elevation of point B.