Determine grade of line BD for the following tacheometric observations: Height of theodolite at A=1.60m. Reduced level of point A = 80.00m. - Observed vertical angle from A to B= +20 30 Observed vertical angle from A to D=-10 35 K= 100 & C = 0.03 - Middle cross hair reading at rod holed at B = 2.60m. Lower cross hair reading at rod holed at B = 1.40m. - Middle cross hair reading at rod holed at D = 2.20m. Upper cross hair reading at rod holed at D = 3.05m. Horizontal angle BAD = 35° 30' 10"