An oil drop carries six electronic charges, has a mass of 1 . 6 1 , 6 x 1 0 ^ 1 2 1 0

An oil drop carries six electronic charges, has a mass of $1.6$x$10^-12$g and falls with a terminal velocity in air. What magnitude of vertical electric field is required to make the drop move upward with the same speed as it was formerly mowing downward?