Read the instructions carefully. This is a simulation exercise using a queue data structure. Imagine that there is a post office or other business which has just one waiting line to serve customers. There is a fixed probability that one new customer arrives each second during the hours of operation for one day. The teller is always available, never takes a break.
All customers wait patiently until they get to the front of the line.
At the end of the working day, the teller leaves immediately, with customers still in line left unserved. Declare a queue and make it empty. If the queue is not empty, increase the counter indicating the number of seconds that has been devoted to the current customer by 1 second. If this value now equals the required service time of the current customer, remove that customer from the queue. Display some information so you can see your program in action.