$[$Formulation Only$][5$ points$]$ The West Hartford Senior Center is trying to establish a transportation system of small and large vans. It can spend no more than $$100,000$ for both sizes of vehicles and no more than $$500$ per maintain it for $$100$ per month. ThS can purchase a small van, which carries up to $7$ passengers, for $$10,000$ and maintained for $$75$ per month. How large vans, which carry up to $15$ passengers, cost $$20,000$ each and can be number of passengers? Please form