Answer:
1170
Step-by-step explanation:P_0=860
P
0
=860
The initial population
t=4
t=4
Time elapsed
d=9
d=9
The doubling time
P_t = P_0\cdot 2^{\frac{t}{d}}
P
t
=P
0
⋅2
d
t
P_t=860\cdot 2^\frac{4}{9}
P
t
=860⋅2
9
4
Plug in
P_t=1170.2794\approx1170
P
t
=1170.2794≈1170