for a) I am unsure:-( I’m sorry, maybe use a graphing calculator..but no one ever owns that lol but for b) you would plug 0 for n because no years have passed so it’s would be P=1250(1.013)^0 which will give you 1250 then for c) you would put 5 for n because you are estimating the population in 5 years so P=1250(1.013)^5 which will give you 1333.39.