During a performance, a cable raises a lighting rig vertically at constant speed. The cable exerts an upward force of 2800 N. The lamps attached to the rig have a total mass of 70 kg. The gravitational field strength is 10 N kg−110\ \mathrm{N\,kg^{-1}}10 Nkg−1. What is the weight of the lighting rig without the lamps?
2800 N−70 N2800\ \mathrm{N}-70\ \mathrm{N}2800 N−70 N
2800 N+(70 kg×10 N kg−1)2800\ \mathrm{N}+(70\ \mathrm{kg}\times10\ \mathrm{N\,kg^{-1}})2800 N+(70 kg×10 Nkg−1)
70 kg×10 N kg−170\ \mathrm{kg}\times10\ \mathrm{N\,kg^{-1}}70 kg×10 Nkg−1
2800 N−(70 kg×10 N kg−1)2800\ \mathrm{N}-(70\ \mathrm{kg}\times10\ \mathrm{N\,kg^{-1}})2800 N−(70 kg×10 Nkg−1)