In the United States, the year each coin was minted is printed on the coin. To find the age of a coin, simply subtract the current year from the year printed on the coin. The ages of circulating pennies are right skewed. Most circulating pennies were minted relatively recently, and extremely old pennies are rare. Assume the ages of circulating pennies have a mean of 12.2 years and a standard deviation of 9.9 years.
a. Based on the information given, can we determine the probability that a randomly selected penny is over 10 years old?
b. What is the probability that a random sample of 40 circulating pennies has a mean less than 10 years?
c. What is the probability that a random sample of 40 circulating pennies has a mean greater than 10 years?
d. What is the probability that a random sample of 40 circulating pennies has a mean greater than 15 years? Would this be unusual?