Many ancient tombs were cut from limestone rock that contained uranium. Since most such tombs are not well-ventilated, they may contain radon gas. In one study, the radon levels in a sample of 12 tombs in a particular region were measured in becquerels per cubic meter (Bq divided by m cubed ). For this data, assume that x overbarequals3 comma 720 Bq divided by m cubed and sequals1 comma 131 Bq divided by m cubed. Use this information to estimate, with 95% confidence, the true mean level of radon exposure in tombs in the region. Interpret the resulting interval.