Which two ways are the most cost-effective to ensure that this new application is implemented properly?

The enterprise customer ABC Corp will deploy a centralized unified communications application to provide voice, and instant messaging to their branch offices. Some of the branch offices are located in remote locations and are connected via a 1.5 Mb/s Layer 3 VPN connection.

Which two ways are the most cost-effective to ensure that this new application is implemented properly? (Choose two)
A . Use a low bitrate codec such as G 711
B . Set voice activity detection to avoid sending packets when the conversations is silent
C . Enable VRF-Lite on the CE router to create a separate voice VRF
D . Set LFI on the WAN connections to interleave the small voice packets with the large data packets
E . Set WAN optimization on the CE router to compress the voice packets for improved bandwidth utilization and performance
F . Use a low bitrate codec such as G 729

Answer: B,F