Electricity and potential energy

[wadini]

Two point charges of magnitude 5.21 nC and -2.24 nC are separated by 29.6 cm. The columb content is 8.98755*10 ^9 N*m^2/C^2. What is the electric potential at a point midway between the charges? Answer in untis of V

I got the answer for this part= 180.36 V

The second part of the question asks what is the potential energy of the pair of charges? Answer in units of N*m. That is where I am confused

 

[rl.bhat]

Potential energy of the system = k*q1*q2/d

 

[wadini]

I don't think you square d. I think it is just d. It doesn't make sense if I want to get it in units of N*m

 

[rl.bhat]

Yes. You are right.