3. [-/3 Points] DETAILS An isotope of a radioactive element has decay constant equal to 0.09 per year. Initially, there are 5 million atoms of the isotope present. Since the isotope decays exponentially, the number of atoms obeys the following equation P = 5e-0.09t In this question, time is measured in years and the number of atoms, P, is measured in millions. a. What is the value of the decay constant? Decay constant : b. What is the half-life of the isotope? per year. (Enter your answer correct to two decimal places.) Half-life: years. c. How many million atoms will be present after 6 years have passed? (Enter your answer correct to one decimal place.) Number present after 6 years: million. Submit Answer 4. [-/3 Points] DETAILS An isotope of a radioactive element has half-life equal to 7 thousand years. Imagine a sample that is so old that most of its radioactive atoms have decayed, leaving just 30 percent of the initial quantity of the isotope remaining. How old is the sample? Give your answer in thousands of years, correct to one decimal place. Age: thousand years.