Ataco truck is parked at a local lunch site and customers queue up to buy tacos at a rate of one per minute. the arrivals of customers are completely independent of one another. it takes 40 seconds on average to serve a customer (using a single server), with a standard deviation of 20 seconds. determine the average time (in seconds) it takes a customer from when they arrive to the truck until they receive their taco. (enter an integer answer.)