Electric Potential of charges on a rectangle

[Extra]

Homework Statement

Consider charges placed at the corners of a rectangle. This rectangle is a horizontal rectangle and is .43 m long and .25 m wide. At the upper right corner there is a charge of 7.0 µC. At the bottom right there is a charge of -14 µC. At the bottom left there is a charge of -8.0 µC. At the upper left there is Point P.
Find the electric potential at point P due to the grouping of charges at the other corners of the rectangle.
Answer in units of V.

Homework Equations

These may help:
EP = -qE(omega)d
PE=kq/r

The Attempt at a Solution

I worked the Potential Energy (so I thought) for point P and drew it out. Then I added the results vectorily, yet, I still got it wrong 5 times. If you could help that'd be awesome.

 

[kuruman]

I worked the Potential Energy (so I thought) for point P and drew it out. Then I added the results vectorily, yet, I still got it wrong 5 times. If you could help that'd be awesome.

Potential energy is a scalar, not a vector. There is nothing to "draw out". You should just add the kq/r terms for each charge because all that matters is the distance to point P not the direction.