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.
| Time (h) | 0 | 8 | 16 | 24 | 32 | 40 | 48 |
| Amount (g) | 5.58 | 5.49 | 5.36 | 5.16 | 4.99 | 4.9 | 4.73 |
(a) Find an appropriate exponential model of the data points.
Amount at time , .
(b) Find the half-life of idoine-131 according to the exponential model in part (a).
Half-life, .
You can earn partial credit on this problem.