A → B is a first order reaction. Using the data below, what is the half-life in seconds? 0 sec, [A] = 1.22 M 3 sec, [A] = 0.86 M 6 sec, [A] = 0.61 M 9 sec, [A] = 0.43 M 12 sec, [A] = 0.31 M 15 sec, [A] = 0.22 M 18 sec, [A] = 0.15 M