Nail spa is a small shop on campus that provides manicures and pedicures. Customer arrival follows a poisson process, at an average rate of 2 customers per hour. 60% of the customers want only a manicure, 40% of the customers want only a pedicure. No customer wants both a manicure and pedicure. Due to different requirements from different customers, the service time varies. The service time of a manicure follows an exponential distribution, and it takes 40 minutes, on average, to do manicure. The service time of a pedicure follows an exponential distribution, and it takes 40 minutes, on average, to do pedicure. The shop hires two employees. Manicure customers are served by employee A, following the first-come-first-served service rule. Pedicure customers are served by employee B, following the first-come-first-served rule. If a customer arrives and cannot be served immediately, the customer will wait in the waiting area.

B) What is the average number of customers waiting in the waiting area? PLEASE SHOW YOUR WORK