A tugboat traveling at 40 kph leaves port at 4 PM carrying off some contraband goods. A patrol boat assigned to stop the goods leaves the same post an hour later and drove at 90 kph. What time will the patrol boat overtake the tugboat?

A tugboat traveling at 40 kph leaves port at 4 PM carrying off some contraband goods. A patrol boat assigned to stop the goods leaves the same post an hour later and drove at 90 kph. What time will the patrol boat overtake the tugboat?