Suppose the human trait for dimples is controlled by a simple dominant and recessive relationship at one locus. Dimples, D, is the dominant allele, and a lack of dimples, d, is the recessive allele. In a college genetics class, the professor takes a tally of students who have dimples and of students with a lack of dimples. In this class of 131 students, 52 have dimples. Calculate the frequency of the dominant allele, D, and the heterozygous genotype, Dd. Express the frequencies in decimal form rounded to the nearest thousandth. Assume the class is in Hardy–Weinberg equilibrium for this trait.

a. Frequency of D = ___.
b. Frequency of Dd = __.