Twins Ron and Roy and their humanoid robot Rob go for a walk in the Sahara. Rob looks like the brothers.
Ron can run at 20 km/h in the desert, Rob 5 km/h slower, and Roy never tried.

Suddenly, they see a lion at a distance of 300 meters, who is the desert sprint champion with the record speed of 30 km/h at a distance of 1 km.

What is the smallest safe speed for Roy to run to their car that is at a distance of 600 meters?