If the half-life for the isotope is 100,000 years, how old is your rock? (To answer this question: please answer the other question on the lab first: " You have collected some samples while examining local rocks. You decide to have them analyzed at WSU using radiometric age dating. Your analysis returns and says that 25% of the parent isotope remains in your rock samples. How many half lives have elapsed? ")

1. 50,000 years old
2. 100,000 years old
3. 200,000 years old
4. 300,000 years old