A small call center normally has 4 employees answering calls while open. On average 6 calls arrive every 4 minutes. Under normal operating conditions each employee on average handles each call in 3.4 minutes. But today one employee has a flu and they need to operate with 3 epmployees during this time. The manager is nervous that they maybe supply constrained and so she directs her employees to hurry up their processing of calls today.
What is the maximum processing average time for each call that they need to achieve today so that they have stable queue?
Round to one decimal place.