I have no clue how to start this problem. The professor wrote: "Write the charge density of a ring." ...and that's it. I know it would probably be ρ as a function of the radius. But I don't know how to move forward. I was looking through the early section in Griffith's E&M Ch. 3 (That's where we are now) and it's roughly covering Laplace's Equation...so I think I need to start there, but I dunno. I'm confused because it doensn't ask for a specific point of reference like you would ordinarily get in a general E&M problem.