Use the Following to Answer Questions

Multiple Choice

Use the following to answer questions :
There are two species of microbes,A and B,which can be grown together or separately.If G_A is the per capita growth rate of species A,G_B is the per capita growth rate of species B,D_A is the density of species A,and D_B is the density of species B,the per capita growth rates for each are the following:
G_A = 0.18 - 0.019 D_A + 0.008 D_B
G_B = 0.22 - 0.012 D_B + 0.005 D_A
-If the density of A is 10 and the density of B is 20,the growth rate(s) of

A) A and B are both positive.
B) A is positive and of B is zero.
C) A is positive and of B is negative.
D) A is negative and of B is positive.
E) A and B are both negative.