Hello, I have this task: Exchange have 1820 subscribers, from them have 1500 DTMF dialing. Receivers will be less then subscribers. Average subscriber creates in busy hour load 0,22 erlangs and mean holding time is 3 minutes. The time, for which is DTMF receiver used is 8,7 seconds. How much receivers must be for max blocking of 0,1%. How much receivers will be busy in busy hour?