2. A reciprocal levelling is observed across a wide river and the reciprocal level readings were taken between points A and B as follows. With instrument set up near A, the rod readings on A are 2.283 and 2.285 m. The reciprocal level reading on the opposite side of the river at point B are 3.618, 3.619, 3.621 and 3.622 m. With the instrument set up near B, the rod readings on B are 4.478 and 4.476 m and the rod readings on the opposite side of the river at point A are 3.143, 3.140, 3.146 and 3.144 m. a. Compute the difference in elevation between A and B with the instrument set up near A. b. What is the true difference in elevation between A and B? c. If the elevation of A is 300 m, what is the elevation of B?