Hi, kindly help me with how to solve this problem. I've seen some solutions, but I still don't understand :/ A sample of the reading scores of 35 fifth-graders has a mean of 82. The standard deviation...

Hi, kindly help me with how to solve this problem. I've seen some solutions, but I still don't understand :/

A sample of the reading scores of 35 fifth-graders has a mean of 82. The standard deviation of the sample is 15.
a) Find the 95% confidence interval of the mean reading scores of all fifth-graders.

b) Find the 99% confidence interval of the mean reading scores of all fifth-graders.

c) Which interval is larger? Explain why