In Drosophila, a recessive mutation called chocolate (c) causes the eyes to be darkly pigmented. The mutant phenotype is indistinguishable from that of an autosomal recessive mutation called brown (bw). A cross of chocolate- eyed females to homozygous brown males yielded wild-type F₁ females and darkly pigmented F₁ males. If the F₁ flies are intercrossed, what types of progeny are expected, and in what proportions? (Assume that the double mutant combination has the same phenotype as either of the single mutants alone.)