500 g of iodine-131 is decaying exponentially. After 3 days 386 g of iodine-131 is left.
(a) Write a function in the form y = y₀e^kt giving the number of grams of iodine-131 after t days.
(b) Write the function from part (a) in the form y = y₀^{(386/500)ƒ(t)}.
(c) Use your answer from part (a) to find the half-life of iodine- 131.