How many people applying for unemployment compensation?

At the height of the great recession of 2009, an average of 120 people arrived each hour at the Philadelphia location for the Pennsylvania unemployment office. To complete the process of applying for unemployment compensation, the applicant must go through three stations. Each station has a single person working at it. The service times at each station are exponentially distributed. The mean times required to complete the process at each station are:

Station 1: 20 seconds

Station 2: 15 seconds

Station 3: 12 seconds

Question: How many people, on average, will be present in the office applying for unemployment compensation?