Bonnie Rogers, the customer relations manager for a large computer manufacturer, has recently studied the duration of telephone calls received by the company's technical support department. The call lengths are exponentially distributed, with a mean duration of 8 minutes. Experience has taught Bonnie that lengthy calls usually can be more efficiently handled by a technical support manager, rather than by the less experienced personnel who receive the initial technical inquiry.
To avoid having the higher-paid managers virtually take over the task of handling technical support, Bonnie would like to have only the longest 10% of the calls redirected to a technical support manager. How long must a technical support call last before it qualifies for redirection to a technical support manager?