Three-point charge Q1 = +10 x 10^-12C, Q2 = -6.0 x 10^-12C and Q3 +10 x 10^-12C are situated at the corners of an equilateral triangle of side 10 m in vacuum. The electric potential at the centre of the triangle is ___.

• A.10 x 10^-3 v
• B.5 x 10^-3 v
• C.6.5 x 10^-3 v
• D.21.8 x 10^-3 v