The officers of a high school senior class are planning to rent buses and vans for a class trip. Each bus can transport 63 students, requires 5 chaperones, and costs $1,400 to rent. Each van can transport 9 students, requires 1 chaperone, and costs $100 to rent. Since there are 756 students in the senior class that may be eligible to go on the trip, the officers must plan to accommodate at least 756 students. Since only 70 parents have volunteered to serve as chaperones, the officers must plan to use at most 70 chaperones. How many vehicles of each type should the officers rent in order to minimize the transportation costs? What are the minimal transportation costs?