Use Pie or 3.14 to find the volume of the sphere below

Pepe and leo deposits money into their savings account at the end of the month the table shows the account balances. if there pattern of savings continue and neither earns interest nor withdraw any of the money , how will the balance compare after a very long time ?

Which one is the correct answer, and why?

Atown has a population of 12000 and grows at 3.5% every year. what will be the population after 7 years, to the nearest whole number?