Many ancient Egyptian tombs were cut from limestone rock that contained uranium. Since most tombs are not well-ventilated, guards, tour guides, and visitors may be exposed to deadly radon gas. A study of radon exposure in tombs in the Valley of Kings, Luxor, Egypt (recently opened for public tours), was conducted. The radon levels measured in becquerels per cubic meter (Bq/m3 ) in the inner chambers of a sample of 12 tombs were determined. For this data, assume that x = 3643 Bq/m3 and s = 1187 Bq/m3 . Use this information to estimate, with 95% confidence, the true mean level of radon exposure in tombs in the Valley of Kings.