Customers Enter the Waiting Line to Pay for Food as They

Customers enter the waiting line to pay for food as they leave a cafeteria on a first-come,first-served basis.The arrival rate follows a Poisson distribution,while service times follow an exponential distribution.If the average number of arrivals is four per minute and the average service rate of a single server is seven per minute,on average,how much time will elapse from the time a customer enters the line until he/she leaves the cafeteria?

A) 0.67 minute
B) 0.50 minute
C) 0.75 minute
D) 0.33 minute
E) 1.33 minutes