The USA Today reports that the average expenditure on Valentine's Day is $100.89. Do male and female consumers differ in the amounts they spend? The average expenditure in a sample survey of 40 male consumers was $135.67, and the average expenditure in a sample survey of 30 female consumers was $68.64. Based on past surveys, the standard deviation for male consumers is assumed to be $39, and the standard deviation for female consumers is assumed to be $17.

1.What is the point estimate of the difference between the population mean expenditure for males and the population mean expenditure for females (to 2 decimals)?

2. At 99% confidence, what is the margin of error (to 2 decimals)?

3. Develop a 99% confidence interval for the difference between the two population means (to 2 decimals). Use z-table.