A student is performing an experiment to determine the radiation emitted by a radioactive source. He uses a radiation detector and notes the total counts in 5-minute intervals. He repeats this three times with the source in place and three times with the source removed. His results are shown here. What is the average corrected count rate for the source?
- A5 counts / minute
- B9 counts / minute
- C25 counts / minute
- D45 counts / minute