A student is trying to determine the half-life of radioactive iodine-131. He measures the amount of iodine-131 in a sample solution every 8 hours. His data are shown in the table below. Time t Amount of 1311 A (h) (g) 4.80 8 4.66 16 4.51 24 4.39 32 4.29 40 4.14 48 4.04 (a) Make a scatter plot of the data. 5 4 4 3 3 3 3 2 2 2 2 t 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 (b) Use a calculator to find an exponential model. (Round all numerical values to three decimal places.) A(t) = (c) Use your model to find the half-life of iodine-131. (Round your answer to one decimal place.) hr