A. Apply the area 4  stub command to all routers in the area
B. On the ABR, use the area 4 stub command with the no - summary keyword
C. On the ABR, specify a default cost for the area with the area default - cost command
D. On the ABR, use the default - information originate  command to inject a default route into area 4
E. Use the auto - cost command on each router in the area to automatically determine the cost to other OSPF areas

A. Nothing. OSPF will determine the most optimal path for routing data by default.
B. Adjust the hello and dead timers for more rapid detection of link failures.
C. Increase the reference - bandw idth used to calculate the interface default metrics, on all routers in your network.
D. Set the priority values on every broadcast interface to ensure that the designated and backup designated routers are the routers with the most processor and memory  resources.