The amount of a sample remaining after t days is given by the equation cap p times t is equal to cap A times 1 half raised to the t over h power , where cap A is the initial amount of the sample and h is the half-life, in days, of the substance. A sample contains 18 percent of its original amount of Radon- 222 The half-life of Radon- 222 is about 3 point 8 days. Which is the best estimate for the age of the sample?