An airplane is flying through a thundercloud at a height of 1600 m. (Flying at this height is very dangerous because of updrafts, turbulence, and the possibility of electric discharge.) If there are charge concentrations of +40.0 C at a height of 3550 m within the cloud and -40.0 C at a height of 1000 m, what is the electric field vector E at the aircraft? (Give the magnitude and direction.)