Bob Nale is the owner of Nale's Quick Fill. Bob would like to estimate the mean number of gallons of gasoline sold to his customers. Assume the number of gallons sold follows the normal distribution with a population standard deviation of 2.30 gallons. From his records, he selects a random sample of 70 sales and finds the mean number of gallons sold is 6.20. (Use t Distribution Table & z Distribution Table.) Required: a. What is the point estimate of the population mean? (Round your answer to 2 decimal places.) Point estimate b. Develop a 90% confidence interval for the population mean. (Round z- score and your answers to 2 decimal places.) and Confidence interval