An oil drop has a mass of 4.2 10-14 kg and a net charge of -4.8 10-19 C. An upward electric force just balances the downward force of gravity, so the...

An oil drop has a mass of 4.2 × 10-14 kg and a net charge of -4.8 × 10-19 C. An upward electric force just balances the downward force of gravity, so the oil drop is stationary. The magnitude and direction of the electric field must be...?