This may be basic.
What is the cost of voting a proxy…What is a cost benefit analysis of proxy voting.
Because you have to vote proxies responsibly, the cost of voting a proxy is the cost of due diligence (e.g., paying someone to do research).
A cost-benefit analysis is weighing that cost against the possible value that can accrue to your clients should the vote be favorable to them.
If the cost of due diligence exceeds the maximum benefit that can accrue to your clients, then voting the proxies is a breach of your fiduciary duty.
Thank you sir. This really helps!!!
I am not sure this was explained so clearly in Shweser notes 
You’re quite welcome.