A research firm conducted a survey to determine the mean repair cost on refrigerators. They found that the distribution of repair costs followed the normal distribution with a population standard deviation of $15.07, A random sample of 50 refrigerators had a mean repair cost of $65 00. Round your answer in part (a) to 2 decimal places. (a] What is the critical z-value that will need to be used to calculate the 95% confidence interval? Round your answers in part (b) to 2 decimal places. (b) What is the 95% confidence interval