In an effort to estimate the mean amount spent per customer for dinner at a major Atlanta

Question:

In an effort to estimate the mean amount spent per customer for dinner at a major Atlanta restaurant, data were collected for a sample of 49 customers. Assume a population standard deviation of $5.
a. At 95% confidence, what is the margin of error?
b. If the sample mean is $24.80, what is the 95% confidence interval for the population mean?