15. A particle of mass 4 x 10-15 kg and charge -5 x 10-C is projected into a region where the electric field is 8 x 103j N/C. If the initial velocity of the particle is (4 x 105i + 2 x 10'j) m/'s, what will be its speed after moving for 5 x 10-s in this region? A. 10 x 10' m/'s B. 3 x 105 m/'s C. 8 x 10' m/s D. 4 x 103 m/'s E. 5 x 10' m/'s Ans: E