if ecoli was allowed to grow for 80 minutes then what would be the propotion of light and hybrid density of Dna molecule?

E.coli divides in every 20 minutes. Thus in 80 minutes 4 generations of bacteria will be obtained. Here red colour is heavy DNA, green is light DNA and DNA with two colours represents hybrid. As picture shows, after 80 minutes the proportion of light and hybrid density of DNA in E.coli is 3:1.