Let say you had 1kg of radioactive material that produced 10x the lethal level of radiation. Let say this material has a half life of 6 seconds. Question 1: Ho

Let say you had 1kg of radioactive material that produced 10x the lethal level of radiation. Let say this material has a half life of 6 seconds. Question 1: How many seconds until its below lethal levels. Question 2: How many years will it take until the last atom is gone with a probability of 99%?