Alden works in the city and lives in the suburbs with Nikka. Every afternoon, Alden gets on a train that arrives at the suburban station at five in the afternoon. Nikka leaves the house before five...

Alden works in the city and lives in the suburbs with Nikka. Every afternoon, Alden gets on a train that arrives at the suburban station at five in the afternoon. Nikka leaves the house before five and drives at a constant speed to arrive at the train station at exactly 5 PM to pick up Alden. The route that Nikka drives never changes. One Tuesday morning, this routine is interrupted because there is a power failure at work. Alden gets to leave early and catches a train that arrives at the suburban station at 4 PM. Instead of calling Nikka to ask for an earlier pickup, Alden decides to have a little exercise. He begins walking home along the route that Nikka drives, knowing that eventually, Nikka will intercept Alden, and then will make a U-turn. This is indeed, what happens, and Alden ends up arriving at home 10 minutes earlier than on a typical day. Assuming that Alden’s walking speed is constant, the U-turn takes no time, and that Nikka's driving speed is constant, how many minutes did Alden walk?