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). Incoming emails are distributed to 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. When not responding to emails, the lawyers on call are encouraged to actively pursue other cases. How much time on a 10-hour day can a lawyer dedicate to this activity, assuming that the lawyers can instantly switch between emails and working on a case, with no other duties or breaks?