Task: Question Answering
Input (English): Problem: the annual birth and death rate in a country per 1000 are 39.4 and 19.4 respectively. the number of years r in which the population would be doubled assuming there is no emigration or immigration is
Options: a. 20, b. r = 25, c. r = 30, d. r = 35, e. 40
Output (English): d