The electric potential at the dot in the figure is 3160 V. What is charge q?

Hi there!

Recall the equation for electric potential of a point charge:

V = Electric potential (V)
k = Coulomb's Constant(Nm²/C²)

Q = Charge (C)
r = distance (m)

We can begin by solving for the given electric potentials. Remember, charge must be accounted for. Electric potential is also a SCALAR quantity.

Upper right charge's potential:

Lower left charge's potential:

Add the two, and subtract from the total EP at the point:

The remaining charge must have a potential of 2036.25 V, so:

i think the answer is a and b

i wish you luck