JEE Advanced Model Paper 10 with solutions for online practice

Abnormality or damage of any organ in the body can be detected with the help of injecting radioactive isotope of N-13. The decay constant is 0.0693 min–1. If injected sample has activity of 40 microcuries (µCi). Assume that to give the correct resulta minimum activity of 2.5 µCi is required. If medicine is injected at 2:00 pm, what will be the time after that examination of organs are not possible?