Shopping spree. Greg is shopping in a large urban depart- ment store with many floors. He enters the store on the
middle floor from a skyway, and he goes directly to the
credit department. After making sure his credit is good, he
goes up three floors to the housewares department. Then
he goes down five floors to the sporting goods department.
Next, he goes up six floors to the media department. Finally,
he
goes
down ten floors to the main entrance to the store on
the first floor at ground level and leaves to go to another store.
How many floors does this department store have if it has no
basement?