Identify the null and alternative hypotheses for the following problems.
a. The manager of a restaurant believes that it takes a customer less than or equal to 25 minutes to eat lunch.
b. Economists have stated that the marginal propensity to consume is at least 90¢ out of every dollar.
c. It has been stated that 75 out of every 100 people who go to the movies on Saturday night buy popcorn.