Problem 3: The life span of scientific calculator has a normal distribution with a mean of 58 months and a standard deviation of 10 months. The company gives a warranty of 36 months to replace any defective calculator with a new one. Suppose the company makes 1 million calculators per year, how many calculators may be replaced? What do I know? What do I want to find? What do I expect the answer to be? How do I go from what I know to what I want to find? Is the answer consistent with what I expected