Timmy can usually make six paper airplanes in an hour. However, if
he gets interrupted by his parents, he can only make four per hour.
His friend John can make seven paper airplanes per hour.
One day, Timmy and John decide to have a three-hour long
contest to see who can make the most paper airplanes. During the
contest, Timmy is interrupted once every hour. John also had to
take a break and do chores for an hour. How many more paper
airplanes does the winner make?