State the null and alternative hypotheses that would be used to test the following claims:
a. There is a difference between the mean age of employees at two different large companies.
b. The mean of population 1 is greater than the mean of population 2.
c. The mean yield of sunflower seeds per county in North Dakota is less than the mean yield per county in South Dakot a.
d. There is no difference in the mean number of hours spent studying per week between male and female college students.