Three infinite planes of charge, A, B and C, are vertical and parallel to one another. There is a uniform electric field EI, to the left of plane A and a uniform electric field EII, to the right of plane C. The field EI, points to the left and the field EII, points to the right. The signs of the charges on plates A, B and C may :

Two cannon balls weighing 18 kg and 24 kg are chained together and fired horizontally with a velocity of 165 m/s from the top of a 21-m wall. the chain breaks during the flight of the cannonballs and the 18-kg cannonball strikes the ground at t = 1.5 s, at a distance of 240 m from the foot of the wall, and 7 m to the right of the line of fire. determine the position of the other cannonball at that instant. neglect the resistance of the air.