While exploring for oil, it was necessary to carry at least 18tones of supplies and 80 people into a desert region.
Two types of vehicles are available :landmaster and sandrovers. Each landmaster could carry 900kg of supplies and 6 people. Each sandrover could carry 1350kg of supplies and 5 people. If there were only 12 of each type in good running order, find the smallest number of vehicles necessary for this journey.