Answer:
The correct answer is 25 years.
Step-by-step explanation: If the population increases by 3.5 %, and the population to start off with is 4,000, this means the population will increase by 140 people every year. (4,000 x 0.035= 140) 140 x 25= 3,500 thus 4,000+ 3500= 7500... 25 years