Dogs in the GoodDog Obedience School win a blue ribbon for learning how to sit, a green ribbon for learning how to roll over, an
d a white ribbon for learning how to stay. There are 100 dogs in the school. 73 have blue ribbons, 39 have green ribbons, and 62 have white ribbons. 21 have a blue ribbon and a green ribbon; 28 have a green ribbon and a white ribbon; 41 have a blue ribbon and a white ribbon. 14 have all three ribbons. How many dogs have not learned any tricks?
