2) a) 4,000 is invested in an account at bank A, which pays 0.5% compound interest each year. 4,000 is also invested in an account at bank B, which pays 0.5% simple interest each year. At the end of 10 years, how much more interest will have been earned at bank A? b) An animal colony has a disease that reduces its population by 15% each year. If the original population was 40,000, how many animals will there be after 20 years? [6]