In 1800 an undeveloped country had a population of 10 million with birth and death rates of 60 and 52 per thousand per year. The situation continued until 1900, when the death rate instantaneously was reduced to 10, but the birth rate remained constant. In 1980 the birth rate fell to 25, with the death rate remaining constant. Estimate the population for the year 2011 assuming exponential population growth.