How to find electric potential at a point?

[pdrjuarez]

Homework Statement

Three charges are arranged as shown.
Find electric potential energy at reference point (the one that's circled)
How much work would it take to bring in a charge of 1.25 µC from infinity to that point?

Homework Equations

V=kQ/r

E_el=QV

The Attempt at a Solution

So, first I calculated the voltage from the 1.85 µC charge and it came out to about 254,000 V
I did the second charge the same way, the one that's at an angle, and got around 321,000 V.
Then I calculated the net voltage from the points using vectors, and the net came out to be 218,000 V.

So, that's the first part. However, I'm not very sure about this, since my friend is getting something else for the same problem. I know that once I get the voltage right, I can use E_el=QV to find the work needed
So, could anyone tell me if I'm doing the first part right please?

 

[ehild]

Voltage is a scalar quantity.

ehild