Exam 300-510 topic 1 question 136 discussion

Refer to the exhibit. After a recent network implementation project, customer A is performing stress testing to verify network redundancy at the branch office connected to R4. When the link from R2 is shut down as shown, the SLA tracking object fails and the cost of the link between R2 and R4 increases to 100. However, a traceroute operation from a PC in the branch office shows that traffic to HQ is still routed via R2. Which solution corrects the problem and optimizes traffic flow via R3 without creating operational overhead?