Extracted text: In their Geodetic Surveying course, three groups of BSGE students were required to establish new benchmarks within and araund the CSU Ampayon Campus using differential leveling. They need to utilize existing 2nd order benchmarks that were established by NAMRIA in Ampayon and another in Basag. Butuan City. In running a line of levels from Ampayon to Basag, 52 instrument setups oare required for each group, with a backsight and foresight taken from each setup. For each rod reading, the estimated error is± 223 mm. For a certain group, what is the error in the measured elevation difference between the starting and closing benchmarks?