Two point charges of 1 nC and 2 nC are placed at the two corners of...

Two point charges of 1 nC and 2 nC are placed at two corners of an equilateral triangle with side 3 cm. The work done in bringing a 3 nC charge from infinity to the third corner equals the charge times the potential at that point.
Both source charges are at distance 0.03 m from the third corner.
The potential due to the 1 nC charge is $V_1 = \frac{9 \times 10^9 \times 1 \times 10^{-9}}{0.03} = 300$ V
and due to the 2 nC charge is $V_2 = \frac{9 \times 10^9 \times 2 \times 10^{-9}}{0.03} = 600$ V.
Total potential: $V_{total} = 300 + 600 = 900$ V
Work done: $W = 3 \times 10^{-9} \times 900 = 2.7 \times 10^{-6}$ J = 2.7 μJ