A Population of Plants Has a Per Capita Growth Rate

Multiple Choice

A population of plants has a per capita growth rate of -0.15 per year.The presence of a mutualistic earthworm increases the per capita growth rate of the plant by 0.0025 per worm per meter square.What is the minimal density of worms needed to bring the per capita growth rate of the plant to above zero?

A) 16
B) 26
C) 41
D) 61
E) 121