A barbershop staffed with only one barber receives an average of 20 customers per day. The mean service time averages about 20 minutes per customer. Assuming that the customer arrival follows a Poisson distribution and the service time follows an exponential distribution. Answer the following questions knowing that the barber works only for 8 hours a day: If a guy walks into this barbershop, what is the probability that he wouldn't have to wait at all? (2 decimal points)