My call centre handles 400 to 500 calls a day. I have 4 agents dealing with this work load. What should be the avarage number of calls handled by an agent per day, and ideally how many more agent do I need to maintain a 80/20 service level.

My call centre handles 400 to 500 calls a day. I have 4 agents dealing with this work load. What should be the avarage number of calls handled by an agent per day, and ideally how many more agent do I need to maintain a 80/20 service level.