It would be rational to hire a dog walker if the work that you would be doing in the time that you have got by skipping taking the dog out for a walk is going to pay you more than $400.
Explanation:
From the point of view of the time cost of a particular task, it is preferable to skip the task if it is not worth your time.
For that to be applicable, you should be earning more than the economic value that you would have spent otherwise doing the other work.
Hence, any task that pays you more for the time put in should be considered to be worth doing.
