BigBank has invested in upgrading the online user experience to guide customers through self-service for certain tasks without needing to call in. BigBank expects that this will reduce call volume to 15 calls per hour, but the calls that remain will be for more complicated requests. BigBank expects the new average call time to be 30 minutes. Assume both coefficients of variation are equal to

1. What is the average wait time in minutes if they have 9 CSRs?

How many CSRs do they need to keep average wait time under 5 minutes?