A radioactive source has an initial activity of 1000Bq and a half-life of 1.0year. To maintain safety, immediately after every full year 20% of the remaining activity is discarded by removing a portion of the source. What will be the activity of the source immediately after the second such removal (i.e., just after 2years)?
(a) 320Bq
(b) 160Bq
(c) 250Bq
(d) 200Bq