Refer to the exhibit.

All routers in the network are in area 12. with IS-IS running in the default configuration as the IGP To avoid congestion on the link from R1 to R2 the network architect planned for traffic from R1 to R3 to pass through R4 To meet the requirement a network engineer set the metric from R1 to R4 to a cost of 15 but the traffic is still travelling through R2 Which action must the engineer take to resolve the issue?