An isotope of a radioactive element has decay constant equal to 0.09 per year. Initially, there are 4 million atoms of the isotope present. Since the isotope decays exponentially, the number of atoms obeys the following equation . 41.09: P = 46' 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 : :] per year. b. What is the half-life of the isotope? (Enter your answer correct to two decimal places.) Half-life : :] years. c. How many million atoms will be present after 7 years have passed? (Enter your answer correct to one decimal place.) Number present after 7 years : C] million