The treatment time for a high-dose-rate brachytherapy plan with an Iridium-192 source was 300 seconds using a nominal source strength of 10 Ci. The source strength at the time of treatment was 6.71 Ci. How long is the treatment? ( A little hint: Treatment times go up at the same rate as the activity decays. So Tt = T0 e + t where Tt is treatment time on day t and T0 is treatment time on day 0, and t is time difference from each treatment.) Group of answer choices 201 seconds 300 seconds 447 seconds 600 sec This cannot be determined