Can someone please explain it to me ASAP?!!?!!? Exponential Growth.

Roughly 12,000 people in a certain country are diagnosed with thyroid cancer every year, which accounts for 1% of all cancer cases. It occurs in women three times as frequently as in men. Fortunately, thyroid cancer can be treated successfully in many cases with radioactive iodine, or l-131. This unstable form of iodine has a half-life of 8 days and is given in small doses measured in millicuries. 3. Suppose a patient is given an initial dose of 120 millicuries. Find the function that gives the amount of l-131 in the body afterta 0 days. b. How long does it take for the amount of l-131 to reach 15% of the initial dose? c. Finding the initial dose to give a particular patient is a critical calculation. How does the time to reach 15% of the initial dose change if the initial dose is increased by 5%? a. Suppose a patient is given an initial dose of 120 millicuries. Find the function that gives the amount of l-131 in the body aftertz 0 days. y(t) = 120 e ' \"-0356\" (Type an expression. Round coefcients to six decimal places as needed.) b. How long does it take for the amount of l-131 to reach 15% of the initial dose? 15 days (Do not round until the nal answer. Then round to the nearest whole number as needed.)