A sand company delivers sand for playgrounds in small and large containers. A small container requires 1 person to unload and can hold 20 units of sand. A large container requires 3 people to unload and can hold 50 units of sand. Since most playgrounds are small, the number of small containers used must be thrice the number of large containers used. In addition, there must be at least 5 small containers and 3 large containers used. If the company has 100 people available, maximize the amount of sand that they can deliver.