Oxygen-15 has a half-life of 124 seconds. You begin with a 429 mg sample of oxygen-15. You wait 6.20 minutes. What is the total amount of time in seconds? (do not include units in the box; enter your answer to 3 sig figs) How many half-lives occur? (do not include units in the box; enter your answer to 1 sig fig) How many milligrams of O-15 remain after 6.20 minutes? (do not include units in the box; enter your answer to 3 sig figs)