0/1 pt 100 Details The amount of time to complete a physical activity in a PE class is approximately normally distributed with a mean of 39.8 seconds and a standard deviation of 6.4 seconds. a) What is the probability that a randomly chosen student completes the activity in less than 31.7 seconds? b) What is the probability that a randomly chosen student completes the activity in more than 45.6 seconds? c) What proportion of students take between 35.6 and 44.4 seconds to complete the activity? d) 95% of all students finish the activity in less than seconds.