Stuck at this problem.

5. The amount remaining of a certain radioactive substance after t days 5. is A(t) = Aoe -0.025t ', where Ao is the beginning amount. How much do we need to begin with if we want 150 grams after 20 days? Round your answer to one decimal place. (2 points)4. You have $5000 to place in a CD for 15 years. The CD pays 2.6% annual 4. interest, compounded monthly. How much will the CD be worth at the end of 15 years? (2 points)