How does one arrive at the probability of availability of free lines during the busy hour?

One can arrive at the possibility of free lines throughout busy hour using the delay probability of the exchange. This delay probability specifies the delay as a caller may face before his call can be finished. In a delay system the caller is completed to wait till a free line is made available for the completion of the call. It leads to call delay. improvement can be made when the system is act as a loss system in place of a delayed system. Within a loss system, the caller has to repeat a call till the call is maintained. It reduces the delay by releasing a caller from the queue till there is repeated action.