A Radioactive Sample Has an Initial Activity of 2 $\times$ 10⁶ Cpm (Counts Per Minute),and After 4

Multiple Choice

A radioactive sample has an initial activity of 2.00 $\times$ 10⁶ cpm (counts per minute) ,and after 4.0 days,its activity is 9.0 $\times$ 10⁵ cpm.What is its activity after 29 days?

A) 8.7 cpm
B) 6.1 $\times$ 10³ cpm
C) 3.3 $\times$ 10² cpm
D) 1.5 $\times$ 10^-9 cpm
E) none of these