Answer:
12 units
Explanation:
Original F = C q1q2/r^2 now change the parameters
New F = C 1/3 q1 2 q2 / (2r)^2
= 2/12 C q1q2/r^2 <=======the new force is 1/6 of original
1/6 * 72 = 12 units
Are there options, because I believe the answer is D.
The choice of path should make no difference. The work should depend only on the end points and not on the route between them. But just to make sure, could we please have a look at the accompanying figure ?