A rancher wants to increase the weaning weights of his cattle herd. A DNA genetic marker with two alleles, A and a, associates with weaning weight. The genotypes have average weaning weights of AA 600 lbs., Aa 500 lbs., and aa 450 lbs. Considering the AA genotype as having maximum fitness (w=1), calculate the fitness and selection coefficients (s) for the Aa and aa genotypes.