On its current web site, the Population Reference Bureau1 offers a comparison between two countries, Italy and the Democratic Republic of the Congo in central Africa. Both countries had similar-sized populations in mid-2008, as shown in the following table. However, the two countries could not be more unlike one another in other demographic parameters. For example, the crude birth and death rates (B and D) for Italy are currently 9 and 10 per 1,000 persons, respectively. The comparable crude birth and death rates for the Democratic Republic of the Congo are 44 and 13 per 1,000 persons, respectively. What is the doubling time (in years) for the Democratic Republic of the Congo ?