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4. A self-propelled tamping foot compactor will be used to compact a fill being constructed of clay material. Field tests have shown that the required density can be achieved with four passes of the roller operating at an average speed of 3 mph. The compacted lift will have a thickness of 6 in. The compacting width of this machine is 7 ft. One bank cubic yard equal to 0.83 ccy. The scraper production, estimated for the project, is 510 bcy/hr. How many rollers will be required to maintain this production? Assume a 50-min hour efficiency