+20 Forty grams of Iodine 131, a radioactive material, decays according to the equation A(t) = 40e^-0.087t (t is in days and A is the amount present at time t)
a. How much iodine 131 is remaining after 5 days?
b. When will 10 grams of iodine 131 be left?
Thank you~~~
