3. A sample of a radioactive isotope is found to have an activity of 115.0 Bq immediately after it is pulled from the reactor that formed it. Its activity 2 h 15 min later is measured to be 85.2 Bq. (a) Calculate the decay constant 7 and the half-life t1/2 of the sample. (b) How many radioactive nuclei were there in the sample initially?

3. A sample of a radioactive isotope is found to have an activity of 115.0 Bq immediately after it is pulled from the reactor that formed it. Its activity 2 h 15 min later is measured to be 85.2 Bq. (a) Calculate the decay constant 7 and the half-life t1/2 of the sample. (b) How many radioactive nuclei were there in the sample initially?