(AP) — Billionaire Warren Buffett says he hopes his son’s new book about his efforts to fight hunger will inspire other people to get involved and make smart choices with philanthropy.

Buffett appeared alongside his son, Howard G. Buffett, and grandson, Howard W. Buffett, on Bloomberg television Tuesday. The men gave several interviews promoting the younger Buffetts’ new book “40 Chances: Finding Hope in a Hungry World.”

Warren Buffett says one of the challenges of philanthropy is there really isn’t a competitive market to test what ideas are working, so donors have to be smart.

Buffett is gradually giving his fortune to five foundations and entrusting them to distribute it, and each of his three children run one of the foundations.