Pumpkin breeding?

Pumpkins defective in the synthesis of orange pigment are pure white. You mate a purebreeding white-pumpkin plant with a pure-breeding white-pumpkin plant from a friend’s pumpkin patch. You are surprised to see that all of the F1 pumpkins are orange. When you mate F1 pumpkin plants with each other, you observe the production of 91 orange-pumpkin plants and 69 white-pumpkin plants in the F2. Explain these results and indicate the genotypes of the parental plants, the F1s, the orange F2s, and the white F2s. Be sure to define your symbols.