Iridium-192 is one radioisotope used in brachytherapy, in which a radioactive source is placed inside a patient's body to treat cancer. Brachytherapy allows the use of a higher than normal dose to be placed near the tumor while lowering the risk of damage to healthy tissue. Iridium-192 is often used in the head or breast. Answer the following three questions (a, b, and c) based on the radioactive decay curve of iridium-192, shown below. Click on the graph and move the mouse over a point to get values for that point.

Could not upload graph but at 150 days, 24.46% of the sample is remaining.

a) If the initial sample is 1.25 g, what mass of the original iridium-192 remains after 150 days?

b) Estimate the half-life of the radioisotope.

c) How many days would it take for three-fourths of the sample to decay?