1A) (Module 1 (Process Analysis)) There are two streams of customers arriving independently at a supermarket: "Express" customers arrive at a rate 80 per hour and stay on average 10 minutes within the shop. Each of them spends on average $25. "Regular" customers arrive at a rate 40 per hour. They stay within the shop for 30 minutes, spending $90 (on average).

a) What is the expected number of "express" customers in the supermarket, at any given point in time? What is the expected total number of customers at the supermarket, at any given point in time?

b) What is the average revenue per hour?