A scientist is working with a substance that has a half-life of 3 years. She starts with 80 grams of the substance. She models the decay using the function \( A(t) = A_0 \left(\frac{1}{2}\right)^{\frac{t}{3}} \), where \( A(t) \) represents the amount of substance remaining after \( t \) years, and \( A_0 \) is the initial amount of the substance. How much of the substance remains after 9 years? Let's think step by step and output the final answer within \boxed{}.
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