Nernst potentials HELP FAST!

[madbeemer]

I know the following
ion/inside cell/outside cell
Cl- 5mM 150 mM
K+ 130mM 5mM
Na+ 20mM 140mM
Ca2+ 10^-4mM 2mM

How would I find the reversal potential for conductance equally permeable to sodium and potassium?
How do I find the reversal potential for a conductance equally permeable to sodium, potassium, and chlorine?

[madbeemer]

Do you use nernst? lol Help please. Not sure how to go about this.