Solve the Problem. -In the Formula a = I , a Is

Multiple Choice

Solve the problem.
-In the formula A = I , A is the amount of radioactive material remaining from an initial amount I at a given time t and k is a negative constant determined by the nature of the material. A certain radioactive isotope has a half-life of approximately 850 years. How many years would be required for a given amount of this isotope to decay to 45% of that amount?

A) 979 yr
B) 733 yr
C) 467.5 yr
D) 934 yr