Acharge q of 7.3 × 10^15 coulomb moves from point a to point b in an electric field. if the potential energy of the charge at point a is 3.5 × 10^-12 joules and that at point b is 1.3 × 10^-12 joules, what is the potential difference between point a and b?

a. 1.3 × 10^2 volts
b. 3.0 × 10^2 volts
c. 3.5 × 10^3 volts
d. 6.8 × 10^3 volts