The order of genes on a plant chromosome is a, b, and d, where a and b have a recombination frequency of 0.2, and b and d have a recombination frequency of 0.3. a pure-breeding plant that has the dominant a and b phenotypes with a recessive d phenotype is crossed to a pure-breeding plant that has the recessive a and b phenotypes with the dominant d phenotype. the resulting hybrid is crossed to a plant that has all three recessive phenotypes. under the assumption that interference in this region is zero, what percentage of each progeny type would result from a single crossover between a and b?