A charge 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 � 102 volts
b. 3.0 � 102 volts
c. 3.5 � 103 volts
d. 6.8 � 103 volts