The Federal Reserve reports that the mean lifespan of a five dollar bill is 4.9 years. Let's suppose that the standard deviation is 1.8 years and that the distribution of lifespans is normal
Find:
(a) the probability that a $5 bill will last less than 6 years.
(b) the probability that a $5 bill will last between 3 and 5 years.
(c) the 98th percentile for the lifespan of these bills (a time such that 98% of bills last less than that time).
(d) the probability that a random sample of 35 bills has a mean length of more than 5.5 years.