A brisk walk at 4 miles per hour bums an average of 300 calories per hour. Assume the variable is normally distributed. If the standard deviation of the distribution is 8 calories, find the probability that a person who walks one hour at the rate of 4 miles per hour will bum the following calories.

a. More than 280 calories.

b. Less than 293 calories.

c. Between 285 and 320 calories.

d. Interpret these probabilities in the context of the problem.