Disaster management

  The county sheriff has a search-and-rescue operation to cover an extremely hazardous mountain area. There are searches for hikers in sum­mer, lost skiers in winter, and downed aircraft all year long. The sheriff has two units in this division-one uses mechanized land vehicles and the other uses a helicopter. The board of supervisors asked the sheriff which unit was most effective. Looking over weather records, the sheriff found that the proba­bility of bad weather was 0.25; variable weather 0.5; and good weather 0.25. Under bad weather conditions, search for a missing person required four hours with the land vehicles, and seven hours with the helicopter. As the weather became variable. the land vehicle required three hours and the helicopter two hours. In good weather the land vehicle required two hours and, as might be expected, the helicopter search time dropped to one-half hour. What did the sheriff tell the board of supervisors' Why?