Answer:
1. The total amount in the account if the interest rate for the account is 3% each year is A(1.03) = 800(1.03)^4 + 350(1.03)^3 + 500(1.03)^2 + 600(1.03).
2. How much money was put into the account at the beginning can be determined by setting x=1 in the equation A(x)=800x^4+350x^3+500x^2+600x and solving for A: A=600
3.$200 is added to the account after 5 years, so B(5)=A(5)+200