Two pure-breeding strains of a plant, designated P1 and P2, produce flowers of the same color, which is purple. Each of these strains, when crossed with a pure-breeding strain X, produces F₁ progeny plants that have pink flowers. When pure-breeding P1 and P2 are crossed, the F₁ progeny plants have purple flowers and self-fertilization of the F₁ progeny resulted in 9/16 plants with pink flowers and 7/16 plants with purple flowers. Determine the number of genes in which variable alleles segregate