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  Choose the correct choice from the following choices:
A) 20	B) R=25	C) R=30	D) R=35	E) 40
Suppose the population of the country in current year is 1000.   So annual increase is  1000 + 39.4 - 19.4= 
<gadget id="calculator"> 1000 + 39.4 - 19.4</gadget>
<output>1_020</output>
1020   Hence every year there is an increase of 2%.   2000= 1000(1+(2/100))^n   n=35 Answer is R=35.
<result>D</result>
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