Charged ring and charged particle problem

[steventf]

The Problem is as follows:
A ring of diameter 7.50 is fixed in place and carries a charge of 5.50 uniformly spread over its circumference.

A) How much work does it take to move a tiny 3.80 micro-columb charged ball of mass
2.00g from very far away to the center of the ring?

B) What is the maximum speed it will reach?

-- I honestly have no idea where to start with this problem.--

 

[SammyS]

What is the electric potential at the center of the ring due to the charge on the ring? (Ignore, for a moment, the charged ball.)