At a certain high school, the distribution of backpack weight is approximately normal with mean 19.7 pounds and standard deviation 3.1 pounds. A random sample of 5 backpacks will be selected, and the weight, in pounds, of each backpack will be recorded. For samples of size 5, which of the following is the best interpretation of
a. Probability that the sample mean is within a specific range
b. Probability that a single backpack weighs more than a certain value
c. Probability that the total weight of 5 backpacks exceeds a certain value
d. Probability that the sample standard deviation is within a specific range