The user starts the stop watch by click on the 'Start' button. The time will run, unless the user clicks on the 'Stop' or 'Pause' button. If the user clicks on the 'Pause' button, the watch stops. Afterwards the user could clicks on the 'Continue' button to continue with the time. The 'Book' button, which is visible after the user clicks on the 'Stop' button, can be used to book the time on a task or activity. The functionality of the 'Book' button has to be implemented. For this, the method queryBook() exists in the library 'StopWatchEventsLib'.