If you had the resources to accomplish something great in the world, what would you do?Legendary investor Warren Buffett posed this challenge to his son in 2006, when he announced he was leaving the bulk of his fortune to philanthropy. So, Howard G. Buffett set out to help the most vulnerable people on Earth—nearly a billion individuals who lack basic food security. And Howard has given himself a deadline: forty years to put more than $3 billion to work on this challenge.Ea...