Answer:
Many decisions are taken at the margin
Explanation:
Many decision are taken at the margin.
He makes small changes at the margin in the number of hours spent training on each activity.
Paola and his wife both realise that increasing time spend in the pool will decrease his total triathlon time.
His time is fixed (20hrs) and anytime he wants to spend extra on one activity, i means that he cannot spend time on another (this is known as opportunity cost).
They are both on the same page in terms of trying to improve Paolo's total time (exploiting opportunities to makes themselves better off).
1hour switch in Paolo's point of view isa major change, whereas his wife recommends a wholesale change.
Paolo realises that as he spends more time in the pool improving his swim time, his run and cycle times will take a hit. As he swims more, his improvement is likely to slow down, while spending less time on cycling and running will cost him more in terms of time.
Hence Paolo is looking at the margins.
His wife on the other hand, is not, she is ignoring the interaction, may be forgetting the ncreasing deterioration in terms of time of the other 2 legs
