37. In maize, two plants that are heterozygous for the recessive alleles a and b are crossed, what frequency of double-mutant progeny will appear if a and b are 7.2 map units apart, and both parents carry a and b in trans (configuration)? a. 0.036; b. 0.0625; c. 0.001296 d. 0.005184; e. 0.072.