6. A An isotope of cobalt 60 is used in medical therapy. When the isotope decays to 45% of its initial amount the hospital needs to replace the radioactive isotope for patient safety (as the exposure quired is now too long to be safe). If the half-life of cobalt 60 is 5.24 years how often does the hospital need to replace the cobalt-60? Thinking/Inquiry 4 marks Please Use Application of Expontials Ly A ( + ) = Ao (t ) #/