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 41 male consumers was $135.67, and the average expenditure in a sample survey of 38 female consumers was $68.64. Based on past surveys, the standard deviation for male consumers is assumed to be $30, and the standard deviation for female consumers is assumed to be $18. a. 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)? 67.03 b. At 99% confidence, what is the margin of error (to 2 decimals)? -13.16 c. Develop a 99% confidence interval for the difference between the two population means (to 2 decimals). Use z-table. ( 53.87 Hide Feedback Partially Correct 80.19 )