$1$ point worth $$5,800$ to potential buyers. He could also sell the car now, without completing the additional work, for $$3,800.$ What should he do$?$

He should complete the additional work and sell the car for $$5,800.$

It does not matter which action he takes since the outcome will be the same either way.

He should sell the car now for $$3,800.$

He should keep the car since it wouldn't be rational to spend $$6,400$ restoring a car and then sell it for only $$5,800.$