Crossing true-breeding pea plants with yellow peas with true-breeding plants with green peas yielded an F1 generation with 100% offspring plants with yellow peas. The F1 plants are self-fertilized and produce F2. In a randomly selected set of 1000 peas from F2 you notice the following phenotypic numbers: 640 yellow and 360 green. Using the Hardy-Weinberg principle: What is the observed frequency of the recessive allele in this F2 population