A powerful race car is propelled by a jet engine. It drives straight at a constant velocity of 300km/h when the force pushing it forward (created by the engine) is a constant 4 thousand N. What is the force of air resistance on the car? Assume that all other sources of friction can be ignored. Enter the magnitude (not the sign) of the force in N. For example, if the answer 3 thousand, enter 3000.