My$-$law.com is a recent start$-$up trying to cater to customers in search of legal services who are intimidated by the idea of talking to a lawyer or simply to lazy for entering a law office. Unlike traditional law firms, My$-$law.com allows for extensive interaction between lawyers and their customers via telephone and the internet. This process is used in the upfront part of the customer interaction, largely consisting of answering some basic customer questions prior to entering a formal relationship.

In order to allow customers to interact with the firm$$s lawyers $($in fact, the firm rents out lawyers from the prestigious law firm Cohen, Fisher, Pearson, Terwiesch and Partners$),$ customers are encouraged to send emails to my$-$lawyer@My$-$law.com. From there, the incoming emails are distributed to the lawyer who is currently $$on call$.$ Given the broad skills of the lawyers, each lawyer can respond to each incoming request.

What is the average time a customer has to wait for $($before$)$ the response to her email change?