A group of private schools in the Czech Republic wish to pool their network access requirements to obtain a direct connection to an ISP in Düsseldorf. There are 15 member schools in the Prague metropolitan area. Schools in the urban center near the Charles Bridge have PDH E-3 fiber connections, but schools in the Soviet-constructed apartment blocks ringing the city have at most an E-3 connection using coaxial cable. Testing has shown that the consortium can expect a 20:1 concentration factor for data. What is minimum bearer service to Düsseldorf the group must purchase?