An airplane is flying in horizontal flight at a constant velocity. The weight of the airplane is 40,000 N. The wings produce a lift force that is perpendicular to the wings and a drag force that is parallel to the wings. The engine produces a forward thrust force of 2,000 N. Which of the following statements is true?

a. The lift force on the airplane is zero.
b. The drag force on the airplane is zero.
c. The lift force on the airplane is 42,000 N upward.
d. The drag force on the airplane is 38,000 N downward.
e. The drag force on the airplane is 2,000 N backward.