I need help on this bio question?

in garden peas, one paif of alleles controls the height of the plant and a second pair of alleles controls flower color. the allele for tall (D) is dominant to the allele for dwarf (d), and the allele for purple (P) is dominant to the allele for white (p). A tall plant with purple flowers crossed with a tall plant with purple flowers produces 3/4 tall purple flowers and 1/4 tall white flowers. what is the genotype of the parents?