Four Identical Point Charges (+4 $\pm$ C)are Placed at the Corners of a Square Which Has

Four identical point charges (+4.0 $\pm$ C) are placed at the corners of a square which has 20-cm sides.How much work is required to assemble this charge arrangement starting with each of the charges a very large distance from any of the other charges?

A) +2.9 J
B) +3.9 J
C) +2.2 J
D) +4.3 J
E) +1.9 J