Can I have help with this?

Jenny is a waitress at a restaurant. Let X be random variable that represents the amount each group at a table leaves for a tip. Jenny wants to estimate the mean amount each group at a table leaves for a tip. A random sample of 37 tables had a sample mean tip of x = $6.50. From long experience, she knows o = $2.86. a. Find a 0.85 confidence interval for the population mean tip . What is the value of margin of error? b. Are the requirements needed for your calculation satisfied? Explain clearly. c. Interpret your result from the part a above