Thallium-208 has a half-life of 3.053 min. How long will a sample containing 120.0 µCi of Thallium-208 take to decay to 7.50 µCi?

(1) 6.11 min.

(3) 12.21 min.

(2) 9.36 min.

(4) 18.46 min.

---

Final Answer:

The time required for Thallium-208 to decay to 7.50 µCi is 12.21 minutes.

Thus, the correct answer is (3) 12.21 min.