In humans, a recessive mutation results in rosy red lips. Another recessive mutation causes long, curly lashes. The two genes r and l are on the same chromosome and are 20 mu apart. If two heterozygous individuals cross, what is the fraction of the offspring that will have both red lips and long lashes? Assume the alleles are in trans in the mother and in cis in the father, and no double crossovers occurred.