The half-life of Cesium-137 is 30 years. Suppose the intial radioactivity of a sample is 170-Bq.
i. What is the radioactivity after 8 years? (give the answer with accurancy of 2 decimal places)
ii. After how long will the radioactivity be 18 Bq? (give the answer as number of years with accurancy of 1 decimal place )