Find the elevation of ground beneath the reflector, if the known elevation of instrument is 12.76m, slope distance = 3.76m, angle is about 3˚43ꞌ, instrument height = 2.93m, ground is at 0.987 m.

• A. 18.54m
• B. 81.54m
• C. 18.45m
• D. 18.97m