Math
posted by Priya .
Supplier ontime delivery performance is critical to enabling the buyer’s organization to meet its customer service commitments. Therefore, monitoring supplier delivery times is critical. Based on a great deal of historical data, a manufacturer of personal computers ﬁnds for one of its justintime suppliers that the delivery times are random and well approximated by the Normal distribution with mean 48.2 minutes and standard deviation 13.4 minutes.
(a) What is the probability that a particular delivery will exceed one hour?
(b) Based on part (a), what is the probability that a particular delivery arrives in less than one hour?
(c) What is the probability that the mean time of 5 deliveries will exceed one hour?

in
http://davidmlane.com/normal.html
I entered:
mean  48.2
SD  13.4
click on "above" and enter 60 (for 1 hour) to get
.1893
etc 
78