I really need help with this math problem...

[elleelle]

A credit union needs information concerning the checking account balances of its customers. A random sample of 14 accounts was checked and yielded a mean balance of $664 and a standard deviation of $297. Assume the population has a normal distribution. You will be finding a confidence interval for the true mean checking account balance for all customers of the credit union.
A.) What distribution will be used. Z or T?
B.) Construct a 90% confidence interval. Remember to write the formula before substituting values. Round confidence interval limits to the nearest dollar.
C.) Complete the sentence summarizing the results: We are 90% confident the true mean checking account balance of all the credit union customers is between ______________ and ___________.

I'm really not just looking for the answer. We may have a question just like this on the final so I'd like to know how to do it as well. Any and all help would be greatly appreciated.

[Quendelton]

Since you aren't looking for an answer how far have you got? Start with A.) which do you think should be used? The Z or T stat? How do they differ?

[Link]

Yes. Please take a stab at it and try to justify your answer. We'll help you as long as we see the effort.