Three students made fruit punch to serve at the school carnival.

They mixed together these ingredients to make their fruit punch:

2.5 gallons of pineapple juice,
2.25 gallons of orange juice, and
3.75 gallons of lemonade.
Each glass of fruit punch holds 6 ounces of fruit punch. They will only serve full glasses of fruit punch.

What is the greatest number of full glasses of fruit punch they can serve?