A proton (charge +e = 1.602 x 10-9 C) moves a distance d = 0.50 m in a straight line between points a and b in a linear accelerator. The electric field is uniform along this line, with magnitude E = 1.5 x 107 V/m = 1.5 x 107 N/C in the direction from a to b. Determine (a) the force on the proton; (b) the work done on it by the field: (c) the potential difference Va - Vs?