The amount of a radioactive isotope present in a certain sample at time t is given by A(t)=700e -0.028311 grams, where t years is the time since the initial amount was measured a. Find the initial amount of the isotope that is present in the sample. b. Find the half-life of this isotope. That is, find the number of years until half of the original amount of the isotope remains. a. The initial amount of the isotope that is present in the sample is grams