My-law.com is a recent start-up trying to cater to customers in search of legal services. Between 8am to 6pm emails from new customers arrive at a rate of 10 emails per hour (coefficient of variation for the arrival process is 1). Icnoming emails are distribute dto the lawyers who a recurrently "on call". Given the broad skills of the lawyers, each lawyer can respond to each incoming request. There are always exactly 2 lawyers on call sitting at their desks waiting for incoming emails. It takes a lawyer an average of 10 minutes to write the response email. Since some cases are substantially more complicated than the others, the standard deviation of this is 15 minutes. On average, how many customers are waiting for a response after sending an email?