The info I have is Mu = $6,000 sigma = $1200.

The problem is suppose we randomly sample 64 loans. What is the probability that at most 41 of these will have a dollar amount of $6,000 or more?

I've tried to use the simple Z formula but that leaves me with 0/1200.

I have no idea how to do this, I can't use the other Z formulas because I don't have the information for them, and if I use mu for the sample mean, not sure if I can even though x-bar can be used as an unbiased estimator for mu, I still get a 0 in the numerator.

I know the answer, but not how to get to it.

The answer is .9878.