The principal $P$ is borrowed and the loan's future value $A$ at time $t$ is given. Determine the loan's simple interest rate $r$.
\[
P=\$ 2000.00, A=\$ 2720.00, t=4 \text { years }
\]
\% (Round to the nearest tenth of a percent as needed.)

Step 1 ：We are given the principal amount (P) as $2000.00, the future value of the loan (A) as $2720.00, and the time (t) as 4 years. We are asked to find the simple interest rate (r).

Step 2 ：The formula for simple interest is given by \(A = P(1 + rt)\), where A is the future value of the loan, P is the principal amount, r is the annual interest rate in decimal, and t is the time the money is invested for in years.

Step 3 ：We can rearrange this formula to solve for r: \(r = \frac{A - P}{Pt}\).

Step 4 ：Substituting the given values into this formula, we get \(r = \frac{2720 - 2000}{2000 \times 4}\).

Step 5 ：Solving this equation, we find that \(r = 0.09\).

Step 6 ：To convert this decimal to a percentage, we multiply by 100, giving us an interest rate of 9.0%.

Step 7 ：Final Answer: The loan's simple interest rate is \(\boxed{9.0\%}\).