With a view to developing a policy for telephone use, an employer monitors 10,000 business calls made from the office by his employees. The calls are categorized according to whether they are local or international calls, made a peak rate (morning) or off-peak rate (after 5 pm), and whether a call lasts less than 1 minute, between 1 and 15 minutes (inclusive) or longer than 15 minutes. The results are summarized in Table 1.

a) What is the probability that a call made from the office will be a local call?

b) What is the probability that a call made in peak-rate time lasts 15 minutes or less?

c) What is the probability that an international call made in peak-rate time will have a duration of more than 15 minutes?

d) What is the probability that a call made will be an international call, in peak-rate time and having a duration of more than 15 minutes?

\begin{tabular}{|c|c|c|c|c|} \hline \multirow{2}{*}{ Call duration } & \multicolumn{2}{|c|}{ Local calls } & \multicolumn{2}{c|}{ International calls } \\ \cline { 2 - 5 } & Peak rate & Off-peak rate & Peak rate & Off-peak rate \\ \hline15 minutes & 535 & 954 & 22 & 519 \\ \hline \end{tabular}