A thing that motivates or encourages someone to do something
I believe it’s A I hope this helps!
Answer:
Decision on the margins
Explanation:
Pool time seems to be having a greater effect at the moment, it makes sense for his to spend a bit more time in the pool and a bit less time on the bike.
However, this does not mean that it makes sense for her to spend all his time in the pool and no time on the bike. If he cut out all training on the bike, the value of a little bit of bike training might be higher than the value of the last hour of pool training. Dimitri does not treat biking versus swimming as an all-or-nothing decision. He makes small changes at the margin in the number of hours spent training for each activity.
Also they both realise that his time is fixed (20hrs) and anytime he wants to spend extra on one activit, is time he cannot spend on another (opportunity cost).
They are both trying to improve Dimitri's total time (exploiting opportunities to makes themselves better off).
An assumption that Dimitri realises that as he spends more time in the pool improving his swim time, his run and cycle times will suffer. As he swims more, his improvement is likely to slow down, while spending less time on cycling and running will cost him progressively more in terms of time.
Conclusion Dimitri is looking at the margins. His wife on the other hand, is not, she is ignoring the interaction, may be forgetting the decreasing improvements in swim and increasing deterioration in the other 2 legs.
