The Radioactive Element Polonium Decays According to the Law

Multiple Choice

The radioactive element polonium decays according to the law where Q​₀ is the initial amount and the time t is measured in days. If the amount of polonium left after 560 days is 40 mg, what was the initial amount present? ​

A) The initial amount was 645 mg
B) The initial amount was 642 mg
C) The initial amount was 651 mg
D) The initial amount was 640 mg