how to solve

1. (10 points.) A random sample of 25 customers is taken and their yearly value to the company is calculated. The calculated average value from the sample is $10 and the standard deviation calculated from the sample is $4 (s=$4). Find a 90% confidence interval for the population mean average value. Show all work. 2. (5 points.) Could you have used the results of the previous problem to test the following hypothesis at alpha= 0.05? Ho: mu=$11 vs. Ha: mu not equal to $11 If so, explain why and provide the answer. If not, explain why not. This is a concept question. Do not perform any additional calculations