SOLUTION: I can buy a car today for $5,000 and at the end of one year will be able to sell it for $4,400. The car yields services which I would be willing to give up if offered a lump sum of

Let's think together.


If you buy this car, then after one year, you will get $4,400 after selling it 
(in the next year's dollars, according to the problem's statement), 
plus  1100*1.15 = 1265  in the next year's dollars for possible service.


Here  1100*1.15 = 1265  is $1,100 obtained today and invested at 15%.


So, if you buy the car, in the next year you may have $4,400 + $1,265 = $5,665 in the next year's dollars.



On the other hand, if you do not buy the car and instead invest $5,000 at 15%, your $5,000 dollars will become 

    $5,000*1.15 = $5,750 

of the next year's dollars.


So, comparing these two possible outcomes, $5,665 for buying the car and $5,750 for not buying it, 
what do you choose?


I think you will choose not to buy the car.