The average expenditure on Valentine's Day was expected to be $100.89 (USA Today, February 13, 2006). Do male and female consumers differ in the amounts they spend? The average expenditure in a sample survey of 60 male consumers was $133.71, and the average expenditure in a sample survey of female consumers was $62.21. Based on past surveys, the standard deviation for male consumers is assumed to be $35 , and the standard deviation for female consumers is assumed to be $12 . The z value is 2.576 .

Round your answers to two decimal places.

a.What is the point estimate of the difference between the population mean expenditure for males and the population mean expenditure for females? _____

b.At 99% confidence, what is the margin of error?_____

c.Develop a 99% confidence interval for the difference between the two population means. _____ to ______