In a certain microwave oven on the high power setting, the time it takes a randomly chosen kernel of popcorn to pop is normally distributed with a mean of 140 seconds and a standard deviation of 25 seconds. What percentage of the kernels will fail to pop if the popcorn is cooked for
(a) 2 minutes?
(b) Three minutes?
(c) If you wanted 95 percent of the kernels to pop, what time would you allow?
(d) If you wanted 99 percent to pop?