A wildlife biologist is interested in a warren, which is where a herd (group) of rabbits lives. She notices that the time rate of change in the rabbit population, R, is proportional to the square root of R. When she started her study 3 months ago, there were 100 rabbits in the herd, and they seem to have been increasing at a rate of about 20 rabbits per month. How many rabbits will live in the warren in another 9 months?
A. 848 rabbits
B. 340 rabbits
C. No rabbits; they reached "doomsday" and died out in 6 months
D. 484 rabbits