PARIS (AP) — Tennis star Roger Federer has twice seen AC/DC in concert. And now a member of the rock group has returned the “serve.” Guitarist Angus Young sat in the presidential box at the French Open in Paris. The crowd cheered Young — and he responded with a wave to the audience and to the tennis star. Federer had a star appearance of his own, winning his second-round match yesterday. Federer says it was “a real pleasure” to have Young on hand.