The diameter of hail hitting the ground during a storm is normally distributed with a mean of .5 inch and a standard deviation of .1 inch. What is the probability that:
(a) A hailstone picked up at random will have a diameter greater than .71 inch?
(b) Two hailstones picked up in a row will have diameters greater than .6 inch? (Assume independence of the two diameters.)
(c) By the end of the storm, what proportion of the hailstones would have had diameters greater than .71 inch?