In purebred Labrador retrievers, the dominant fur-color allele, B, results in black fur, and the recessive allele, b, results in yellow fur. Suppose the Happy Labrador Ranch breeds yellow and black Labrador retrievers. The Ranch is expecting a new litter of four puppies, and the owners want to calculate the probability that the puppies will be either all black or two will be black and two will be yellow. The parents of the new litter are both black and

heterozygous, Bb, for coat color.

Calculate the probability that the new puppies will be either all black or two will be black and two will be yellow. Enter the probability as a decimal rounded to the nearest thousandth.