(4 points) In a kind of savings account, the amount of money after 4 years is given by the function A(r) = 5000er where r is the interest rate. If the interest rate is 2%, the amount of money after 4 years is $5,416. When the interest rate is 3.5%, the amount of money after one year is $5,751. What property of this function, and what theorem, guarantees that there is an interest rate between 2% and 3.5% that gives $5,500 in the account