The electric potential of a charged particle is:
V = kq/r
Where:
r → is the distance from the particle to the point.
q → is the charge of the particle.
k = 9*10^9 Nm^2/C^2 → is the constant electric.
For each electric charge, we have the following:
q1 = +2.40 C, r1 = 3.40/2 = 1.7 m
V1 = kq1/r1 = (9*10^9)(2.40)/1.7
V1 = 12.7*10^9 V
q2 = - 6.80 C, r2 = 3.40/2 = 1.7 m
V2 = kq2/r2 = (9*10^9)(-6.80)/1.7
V2 = - 36*10^9 V
VR = V1 + V2 = 12.7*10^9 + (-36*10^9) = - 23.3*10^9 V