An IPCC Express 4.0 deployment requires support for 20 concurrently logged-in agents and three supervisors. The agents are split evenly across two remote sites. High Availability is required for this deployment, and the agents will be using IP Phone Agent as they use Citrix terminals. Silent monitoring and recording will be performed for agents at both sites. No historical reporting will be done during call center open hours. Assume the minimum number of servers is desired.  How many IPCC Express hardware servers would be required for this IPCC Express deployment?（）