If I were in the mood to do your homework ... Without having access to your actual textbook, and what you were taught ... I would think:
Value to you = earnings + disposal value - cost
If you bought a car for NGN500,000 just now, and it's second hand price is NGN400,000 but you can use it as a taxi and earn NGN10,000 a month for 60 months before disposing it for free. How much is it worth to you? Explain your answer briefly
I'll let you do the work in your currency, but assuming the second hand value remains the same and you exclude the cost of any repairs and maintenance and fuel, you would have about $2535 in US dollars when you sold the car after using it for that time.