Rohan and Sanya were out for a bike ride when the tyre on Rohan's bike burst.

They were 20 km from home, so they decided Rohan would walk back while Sanya would take the working bike, leave it further along the road and walk the rest of the way.

When Rohan reached the bike, he would ride it home.

If Rohan walks at 5 km/hr and rides at 12 km/hr and Sanya walks at 4 km/hr and rides at 10 km/hr, how far should Sanya ride the bike for both to arrive home at the same time?