A population x of rabbits on an island is modeled by x' = (1/1000)x^2, where the independent variable is time in months. At time t = 0, there are 40 rabbits on the island.
a) Find the solution to the equation with the initial condition.
b) How many rabbits are on the island in 1 month, 5 months, 10 months, 15 months (round to the nearest integer).