Mark buys an old airplane with the intention of repairing, restoring and selling it. He anticipates it will cost him 295000 to purchase, repair and restore the plane and he can sell the finished plane for 350000. When he has spent a total of 295000 on the project, he discovers that he needs to replace the engine. A new engine costs 100000. He can sell the plane without the new engine for 220000. What should he do.? How much money does he make or lose overall. Refer to marginal cost and benefit of each option.