20 pts to whoever helps!!

The standard deviation of a simple random sample of 40 calling times on a pay phone is found to be 2.6 minutes. Find the statistic to test a claim that the standard deviation of all phone calls on a pay phone is less than 2.9 minutes. Use a 0.05 significance level.
a. 32.152
b. 31.348
c. 48.519
d. 34.966

Which of the following is correct interpretation of the expression -4+13

Walking at a constant rate of 8 kilometers per hour, juan can cross a bridge in 6 minutes. what is the length of the bridge in meters?

Use the given degree of confidence and sample data to construct a confidence interval for the population mean mu . assume that the population has a normal distribution. a laboratory tested twelve chicken eggs and found that the mean amount of cholesterol was 185 milligrams with sequals 17.6 milligrams. a confidence interval of 173.8 mgless than muless than 196.2 mg is constructed for the true mean cholesterol content of all such eggs. it was assumed that the population has a normal distribution. what confidence level does this interval represent?