HINT 17O: Assume that the alleles are combined randomly, in linkage equilibrium; this is a fairly good approximation for unlinked loci. Then, for each pair of allele frequencies, work out the frequencies of the four genotypes and hence the average fitness. By writing out the mean fitness on a grid (say, at *p*_{A}, *p*_{B} = 0, 0.25, 0.5, 0.75, 1), you can sketch the contours of mean fitness.