You drive your car into the parking lot of your favorite fast food establishment and get in the line for drive through service

After placing your order into the speaker, you proceed to the first window to pay, and then to the second window to pick up your meal. Since you just studied waiting lines that day in your Operations Management class, you quickly realize as you drive away that this was an example of a ________ channel ________ phase queuing system.
Fill in the blanks with correct word

single, multiple