The Los Angeles Times (June 14,1995 ) reported that the U.S. Postal Service is
getting speedier, with higher overnight on-time delivery rates than in the
past. Postal Service standards call for overnight delivery within a zone of
about \(60 \mathrm{mi}\) for any first-class letter deposited by the last
collection time posted on a mailbox. Two-day delivery is promised within a 600
-mi zone, and three-day delivery is promised for distances over \(600
\mathrm{mi}\). The Price Waterhouse accounting firm conducted an independent
audit by "seeding" the mail with letters and recording on-time delivery rates
for these letters. Suppose that the results of the Price Waterhouse study were
as follows (these numbers are fictitious, but they are compatible with summary
values given in the article):
$$\begin{array}{lcc}
& \begin{array}{c}
\text { Number } \\
\text { of Letters } \\
\text { Mailed }
\end{array} & \begin{array}{c}
\text { Number of } \\
\text { Letters Arriving } \\
\text { on Time }
\end{array} \\
\hline \text { Los Angeles } & 500 & 425 \\
\text { New York } & 500 & 415 \\
\text { Washington, D.C. } & 500 & 405 \\
\text { Nationwide } & 6000 & 5220
\end{array}$$
Use the given information to estimate the following probabilities:
a. The probability of an on-time delivery in Los Angeles
b. The probability of late delivery in Washington, D.C.
c. The probability that both of two letters mailed in New York are delivered
on time
d. The probability of on-time delivery nationwide