Nuclear medicine is a branchhh hof medicine which uses radioactive materials in diagnosis and therapy. radioactive substances are administered to patients and the radiation emitted is measured. iodine-131 which has a half-life of k days is a substance that is used to diagnose and treat cancers of thhhe thyroid gland. the graph below is an exponential decay for a dose(d) or iodine-131 given to a patient as a function in time in days.

the graph shows the iodine remaining in body (% of dose) from 0-100 starting at 100. and the bottom of the graph is time(days from 0-60) and the graph is dropping with the marked point (24, 12.5)

b) using the point (24, 12.5) , determine the half life k of iodine-131 and write the equation.

c)iodine 131 is unable to be detected after it has decayed 5% of its initial dose. using your equation, determine how many days to the nearest tenth will have passed until the dose is undetectable?

i solved for b, need with c.