A sheet conveying apparatus has a conveyor for conveying a sheet to a prescribed position, a pair of reverse-discharge rotating members capable of rotating forward and reverse for feeding the sheet to the conveyor by switchback and an electricity removal unit for removing electricity from the conveyed sheet. In one embodiment, a plurality of first cost factors associated with a first set of network elements is obtained. A gas block for the firearm includes a spring-loaded plunger assembly positioned within a bore of the gas block and oriented parallel to a bore of a barrel of the firearm, the plunger assembly including a regulator plunger, a regulator bushing, a regulator spring, and a regulator cap.