If the observed back sight and fore sight are x1 and x2. The correction back sight on A will be equal to x1-y1, where y1= D1 tan i . The correct fore sight on B will be equal to x2-y2 where, y2 = D2 tan i . Then what is the correction difference in level between A and B, if D1 = D2?

• A. x1 x2
• B. x2 + x1
• C. x1 x2 + (D2 tan i D1 tan i )
• D. x2 x1 + (D1tan i + D2 tan i )