The Half-Life Of ${ }_{17}^{36} \mathrm{Cl}$ Is 95 × 10¹² S

The half-life of ${ }_{17}^{36} \mathrm{Cl}$ is 9.5 × 10¹² s.How many atoms of ${ }_{17}^{36} \mathrm{Cl}$ are present in a sample with an activity of 3.9 × 10⁹ atoms/s?

A) 1.9 × 10−²³ atoms
B) 4.1 × 10−⁴ atoms
C) 2.4 × 10³ atoms
D) 9.1 × 10¹⁶ atoms
E) 5.3 × 10²² atoms