Puzzle for March 15, 2010

Since yesterday was Pi Day (3.14, get it?), I hope you got some pie!

Village Inn restaurant is famous for the many kinds of pies it makes. The pumpkin pie for example is 8 inches across and serves 5. How many cans of whipped cream do they need to do the outside edge of the pies if they sell 15 pies?

The can of whipped cream will do 36 linear inches