The average monthly gasoline purchase for a family with 2 cars is 85 gallons. This statistic has a normal distribution with a standard deviation of 12 gallons. A family with 2 cars is chosen at random.
(a) Find the probability that the family's monthly gasoline purchases will be between 80 and 90 gallons.
(b) Find the probability that the family's monthly gasoline purchases will be less than 75 gallons.
(c) Find the probability that the family's monthly gasoline purchases will be more than 90 gallons