....................                ,_______________
  |                  |                |              |
  | CONTRACT         |                | VEHICLE      |
  |                  |                |              |
.-| id               '                | id           '........
| . rate_id          .....            | name         |       |
| |                  |   |            `............../       |
| |                  |   |                                   |
| |__________________|   |                                   |
|                        |                                   |
|                        |   ,_____________________          |
|                        |   |                    |          |
|                        |   | RATE               |          |
|                        |   |                    |          |
|                        ....' id                 |          |
-----------------------------. contract_id        |          |
                             | vehicle_id         |..........|
                             | price              |
                             |                    |
                             |                    |
                             |                    |
                             `..................../

   for each contract..there are list of vehicles and price of each
   vehicle.

   idea is that when I do SELECT * from RATE where contract_id = 1
   that will return rows of vehicles and price.