An interrupted mating study is carried out on Hfr strains 1, 2, and 3 identified in Problem 17. After conjugation is established, a small sample of the mixture is collected every minute for 20 minutes to determine the distance between genes on the chromosome. Results for each of the three Hfr strains are shown below. The total duration of conjugation (in minutes) is given for each transferred gene.

Hfr strain 1           oriT     met     ala     lac     gal
Duration (min)       0          2        8       13      17
Hfr strain 2           oriT     met     leu     thr      azi
Duration (min)       0          2        7       10      17
Hfr strain 3           oriT     gal      pro     trp      azi
Duration (min)       0          3        8       14      19

Explain why azi is the last gene of strain 2 to transfer in the 20 minutes of conjugation time. How many minutes of conjugation time would be needed to allow the next gene on the map to transfer from Hfr strain 2?