Provide an Appropriate Response $\$ 157$ With a Standard Deviation Of $\$ 38$

Provide an appropriate response.
-In a random sample of 26 laptop computers, the mean repair cost was $\$ 157$ with a standard deviation of $\$ 38$ . Assume the population has a normal distribution.
a) Construct a $95 \%$ confidence interval for the population mean, $\mu$ .
b) Suppose you did some research on repair costs for laptop computers and found that the standard deviation is $\sigma = 38$ . Use the normal distribution to construct a $95 \%$ confidence interval for the population mean, $\mu$ . Compare the results.