Commutative Ring with Nonzero Prime Ideal P = P2: Example and Proof

[FanofAFan]

Homework Statement

Give an example of a commutative ring R with a 1 and nonzero prime ideal P of R such that P = P²

Homework Equations

The Attempt at a Solution

Letting R be an integral domain and look at the ideal 0xR in RxR. is all i got but not sure how to show this or what to do next

 

[micromass]

Well, you need to show first that 0xR is a prime ideal, and then show that P²=P. How would you approach the first question, that is, showing that it is a prime ideal??