Four point charges, A, B, C, and D, are placed at the corners of a square with side length L. Charges A, B, and C have charge +q, and D has charge ?q.

If you calculate W, the amount of work it took to assemble this charge configuration if the point charges were initially infinitely far apart, you will find that the contribution for each charge is proportional to (kq^2)/L. In the space provided, enter the numeric value that multiplies the above factor, in W.