The physical fitness of an athlete is often measured by how much oxygen the athlete takes in (which is recorded in milliliters per kilogram, ml/kg). The mean maximum oxygen uptake for elite athletes has been found to be 75 with a standard deviation of 6.3. Assume that the distribution is approximately normal.
(a) What is the probability that an elite athlete has a maximum oxygen uptake of at least 65 ml/kg?
(b) What is the probability that an elite athlete has a maximum oxygen uptake of 70 ml/kg or lower?