Identical Point Charges (+20 μC) Are Placed at the Corners

Multiple Choice

Identical point charges (+20 μC) are placed at the corners of an equilateral triangle with sides of 2.0-m length. How much external energy is required to bring a charge of 45 μC from infinity to the midpoint of one side of the triangle?

A) 26 J
B) 16 J
C) 23 J
D) 21 J
E) 12 J