A motor transfers 2400 J usefully. Its efficiency is 0.80. How much energy is dissipated in unwanted transfers?
1920 J1920\ \mathrm{J}1920 J
480 J480\ \mathrm{J}480 J
600 J600\ \mathrm{J}600 J
3000 J3000\ \mathrm{J}3000 J