A survey of a group of 114 tourists was taken in St. Louis. The survey showed the following: 61 of the tourists plan to visit Gateway Arch; 48 plan to visit the zoo; 11 plan to visit the Art Museum and the zoo, but not the gateway Arch; 12 plan to visit the Art Museum and the Gateway Arch, but not the zoo; 18 plan to visit the Gateway Arch and the zoo, but not the Art Museum; 6 plan to visit the Art Museum, the zoo, and the Gateway Arch; 16 plan to visit none of the three places. How many plan to visit the Art Museum only?