How much mass would be required to power a 250 W motor for 4 hours? (Hint: Remember that the Work-Energy Theorem states that work equals a change in energy. First, solve for work to find the energy, which you can then use in the mass-energy equivalence equation.) Group of answer choices 0.003 kg 2.78 x 10-15 kg 8.33 x 10-7 kg 4.0 x 10-11 kg