A researcher recorded the amount of time each patient at a regional medical clinic spent waiting for service during a Tuesday morning. The frequency table at the right summarizes the data collected. First, extend the table to include a relative frequency column. Then, if one of the patients is randomly selected, what is the proabability that the waiting time is less than 15 minutes?

Wating Time (Minutes)	Number of Customers
0-4	9
5-9	22
10-14	28
15-19	11
20-24	3
25-29	2