Which three describe the reasons large OSPF networks use a hierarchical design? (Choose three.)

Which three describe the reasons large OSPF networks use a hierarchical design? (Choose three.)

A. to speed up convergence B. to reduce routing overhead C. to lower costs by replacing routers with distribution layer switches D. to decrease latency by increasing bandwidth E. to confine network instability to single areas of the network F. to reduce the complexity of router configuration