In a 350-m race, runner A starts from rest and accelerates at 1.6 m/s2 for the first 30 m and then runs at constant speed. Runner B starts from rest and accelerates at 2.0 m/s2 for the first 30 m and then runs at constant speed. Runner A begins running as soon as the race begins but B first takes a nap to rest up. What is the longest nap that B can take and still not lose the race?