In trigonometric leveling from point A to point B, the slope distance and zenith angle measured at

Question:

In trigonometric leveling from point A to point B, the slope distance and zenith angle measured at A were 2504.897 m and 85o 08' 54'' At B these measurements were 2504.891 m and 94o 52' 10'' respectively. If the instrument and rod target heights were equal, calculate the difference in elevation from A to B.