You want to leave a time capsule that will be dug up by your descendants in 10,000 years. You want them to have 15g of Niobium-91. How many grams of Niobium-91 should you put in your time capsule? The half-life of Niobium-91 is 680 years.
A) 60 g
B) 30 g
C) 7.5 g
D) 3.75 g