What is a fColumb? Finding Net Electric potential, still wrong

[mr_coffee]

I'm suppose to find the net electric potential at point P due to the four particles, if V = 0 at infinity, q = 5.50 fC, and d = 3.00cm?
THe picture is here: http://www.webassign.net/hrw/hrw7_24-33.gif
I used V = (5.50/.03 + 5.50/.03 - 5.50/.03 - 5.50/(.06));
I noticed that the very end negative charge is 2d away from P not just d. But i only have 2 more chances left to get it right. so i found V = 6.37E-10 V. But I never converted 5.50 fC to just C. So I'm assuming my answer is off slightly, anyone know what fC stands for also, do yuou know if I'm right? Thanks!]

 

[Doc Al]

The potential at a distance r from a point charge is $k q/r$. The prefix "f" stands for femto, which means $10^{-15}$.

 

[robphy]

In the metric system, f= femto=10^{-15}

http://en.wikipedia.org/wiki/Femto

 

[mr_coffee]

awesome, thanks guys, it worked great!