If the maximum tractive effort of a vehicle is 450 lb and the engine generated tractive effort is 425 lb, then the available tractive effort is

When can a theory be modified if a new type of technology allows for new observations that raise new questions? a-immediately, while the questions about the theory are being asked b-after new hypotheses related to the theory are tested in experiments c-only after the new observations disprove all parts of the theory d-while scientists begin to think about how the theory could improve