The constants K and C for a certain instrument were 99.95 and 0 respectively. The ground makes a uniform slope of 9.2% from point A to point B. With the instrument at A and staff at B, readings were taken but due to obstruction in the line of sight, only the reading was recorded to be 1.971. If the vertical angle of the instrument was 6.46 and the height of the instrument above A was 1.65 m, determine the horizontal distance between A and B.