A tumor is injected with 0.8 grams of Iodine-125, which has a decay rate of \( 1.15 \% \) per day. Write an exponential model representing the amount of Iodine-125 remaining in the tumor after \( t \) days. Then use the formula to find the amount of Iodine-125 that would remain in the tumor after 60 days. Enter the exact answer. Enclose arguments of functions in parentheses and include a multiplication sign between terms. For example, \( c^{*} \exp (h) \) or \( c^{*} \ln (h) \).

To model the decay of Iodine-125 in the tumor, we start with the initial amount, \( A_0 = 0.8 \) grams, and a decay rate of \( 1.15\% \) per day, which can be expressed as a decimal \( r = 0.0115 \). The exponential decay model can be represented as: \[ A(t) = A_0 \cdot \exp(-r \cdot t) = 0.8 \cdot \exp(-0.0115 \cdot t) \] Now, to find the amount remaining after 60 days, we plug \( t = 60 \) into the equation: \[ A(60) = 0.8 \cdot \exp(-0.0115 \cdot 60) \] Calculating the exponent: \[ -0.0115 \cdot 60 = -0.69 \] So we find: \[ A(60) = 0.8 \cdot \exp(-0.69) \] Using a calculator for \( \exp(-0.69) \): \[ A(60) \approx 0.8 \cdot 0.5003 \approx 0.40024 \] Thus, the exact amount of Iodine-125 remaining in the tumor after 60 days is approximately \[ 0.4002 \text{ grams (to four decimal places)}. \]