How many hours should it take an articulated wheel loader equipped with a 4-yd (3.06-m ³ ) bucket to load 3000 cu yd (2294 m ³ ) of gravel from a stockpile into rail cars if the average haul distance ft (91.5 m) one way? The area is level with a rolling resistance factor of 120 lb/ton (60 kg/t). Job efficiency is estimated at 50 min/h.