Mary wants to have $$8500$ to travel to South America when she is $21$. She currently has $$6439$ in a savings account earning $4\%$ annual compound interest. Mary is $13$ now.

1. If Mary does not take out or deposit any money, how much money will Mary have when she is $15$?

   Hint (a):

   Formula for compound interest:

   $A = P\left(1 + r\right)^{n}$

   More Help (a):

   $6439\left(1 + 0.04\right)^{2}$

   Answer (a):

   $$6964.4$2

2. Will Mary have enough money for her trip when she is $21$?

   Hint (b):

   Find how much money Mary will have in $8$ years.

   More Help 2(b):

   Is this amount enough?

   More Help 1(b):

   Use the formula in (a).

3. If Mary were to graph this situation, describe what the graph would look like.

   Hint (c):

   Is the amount of money Mary has increasing or decreasing? In what way is it doing so?