<h1>The anxius dog and his boss,Math problem</h1>

This is a mathematical problem that can be solved by simple equations, but it becomes much easier with logic

 

A gentleman returns home with his dog after a stroll.
The master walks 4 kilometers an hour.
Because the dog is anxious, 8 kilometers before it leaves the leash to run home.

The dog runs at a constant speed 10km/h.
Upon arriving at the house, he sees the door closed, immediately changes and returns with the same speed to his boss.
As soon as it arrives, it makes an immediate change and returns running to the house.
These are repeated repeatedly until the master arrives at the house and opens the door.

How many kilometers has the dog done since leaving the leash?