A line graph between truck tires in hundreds and bike tires in hundreds has six points, A to F, marked on it. The coordinates are (0,12), (3,10), (5,8), (7,5), (8,3), (9,0) respectively, and they joined to form a declining line. If the firm is at point D and decides to increase the production of bike tires by 300 units, the opportunity cost will be ------ truck tires. If the firm is at point B and decides to increase the production of truck tires by 400 units, the opportunity cost will be ------ bike tires.