A group of 800 insects invades a region and begins to obey the law of natural ...

A group of 800 insects invades a region and begins to obey the law of natural growth.   Three weeks after the invasion, 1000 insects are present.

a. Approximately how many insects were present one week after the invasion?

b. What was the insect population five weeks after the invasion?

c. Approximately how long does it take the insect population to double?