Writer Garrison Keillor is perhaps best known as the force behind the wildly-popular radio program, “A Prairie Home Companion.” But after retiring from the show, Keillor was accused of sexual misconduct, causing Minnesota Public Radio, the show’s distributor, to sever ties. They have since settled the matter and signed a confidentiality agreement. But Keillor has never stopped writing, and is now back on the road entertaining his audience. Keillor talks with correspondent Anthony Mason about the allegations of inappropriate behavior, aging, and two new books: “Serenity at 70, Gaiety at 80,” and his latest collection of tales from Lake Wobegon, “Boom Town.”