According to the Corporate Travel Index compiled by Business Travel News, the average daily cost for business travel in the United States rose to per day (Executive Travel website). The file Travel contains sample data for an analogous study on the estimated daily living costs for an executive traveling to various international cities. The estimates include a single room at a four-star hotel, beverages, breakfast, taxi fares, and incidental costs. City Daily Living Cost ($) City Daily Living Cost ($)
Bangkok 242.87 Mexico City 212
Bogota 260.93 Milan 284.08
Cairo 194.19 Mumbai 139.16
Dublin 260.76 Paris 436.72
Frankfurt 355.36 Rio de Janeiro 240.87
Hong Kong 346.32 Seoul 310.41
Johannesburg 165.37 Tel Aviv 223.73
Lima 250.08 Toronto 181.25
London 326.76 Warsaw 238.2
Madrid 283.56 Washington, D. C. 250.61

Required:
a. Compute the sample mean.
b. Compute the sample standard deviation.
c. Compute a 95% confidence interval for the population standard deviation.