In an article appearing in Today's Health a writer states that the average number of calories in a serving of popcorn is 76. To determine if the average number of calories in a serving of popcorn is different from 76, a nutritionist selected a random sample of 20 servings of popcorn and computed the sample mean number of calories per serving to be 80 with a sample standard deviation of 6.3. State the null and alternative hypotheses.