A) A stadia reading is recorded to have an upper cross hair reading of 1, 570m and a lower cross hair reading of 1, 490m. The zenith angle is 85 degree 31 02" and the height of instrument is recorded...

A) A stadia reading is recorded to have an upper cross hair reading of 1, 570m and a lower cross hair reading of 1, 490m. The zenith angle is 85 degree 31 02" and the height of instrument is recorded as 1.375m. Calculate the slope distance between the instrument and the staff position and the RL of the ground surface at the staff position if the RL at the instrument location is 42.750m?