Johnny is in point (2,0) and walks to point (-2,0).On his way there’s a pond within the curve $\big|x\big|+\big|y\big|=1$. He walks 5 km/h outside the pond and $\frac{5\sqrt{5}}{2\sqrt{2}}$ km/h within the pond. In which point does he enter the pond, or should he walk around?
I don't know where to start. Does anyone have some tips?