28. An alpha particle (produced in many nuclear reactions) has a mass of 6.64 x 10-27 kg and a charge of +2e. In a uniform electric field inside a linear accelerator, an alpha particle is observed to have an acceleration of 9.5 x 10 m/s. The magnitude of the electric field is (a) 1.35 x 10 N/C; (b) 1.97 x 10 N/C; (c) 3.52 x 10 N/C; (d) 2.50 x 107 N/C.