A customer has two main receptionists using SoftConsole; however, when they are away from their desk, there are two back office workers who have the SoftConsole on their PC to take calls to cover…

A customer has two main receptionists using SoftConsole; however, when they are away from their desk, there are two back office workers who have the SoftConsole on their PC to take calls to cover these periods. How many licenses are required for two of the possible four SoftConsole to work in business hours?