I want to obtain a sample to estimate a population mean. Researchers believe the population standard deviation is approximately 41.7. We would like to be 99.5% confident that the estimate is within 4...

I want to obtain a sample to estimate a population mean.  Researchers believe the population standard deviation is approximately 41.7.  We would like to be 99.5% confident that the estimate is within 4 of the true population mean.  How large of a sample size is required?