The officers of a high school senior class are planning to rent buses and vans for a class trip. Each bus can transport 90 students, requires 2 chaperones, and costs $1,100 to rent. Each van can transport 10 students, requires 1 chaperone, and costs $90 to rent. Since there are 450 students in the senior class that may be eligible to go on the trip, the officers rent in order to minimize the transportation costs? What are the minimal transportation costs?