Hi, I need help in solving this problem. I don't understand how to set up and solve.

When studying radioactive material, a nuclear engineer found that over 365 days, 1,000,000 radioactive atoms decayed to 978,103 radioactive atoms, so 21,897 atoms decayed during 365 days. a. Find the mean number of radioactive atoms that decayed in a day. b. Find the probability that on a given day, 54 radioactive atoms decayed. a. The mean number of radioactive atoms that decay per day is (Round to three decimal places as needed.) b. The probability that on a given day, 54 radioactive atoms decayed, is (Round to six decimal places as needed.) Enter your answer in each of the answer boxes