The Decay Constant,k,for ${ }_{88}^{226} \mathrm{Ra}$ Is 137 × 10−¹¹ S−¹

The decay constant,k,for ${ }_{88}^{226} \mathrm{Ra}$ is 1.37 × 10−¹¹ s−¹.What mass of ${ }_{88}^{226} \mathrm{Ra}$ has an activity of 1.06 × 10⁹ atoms/s?

A) 6.60 × 10−⁶ g
B) 1.49 × 10−³ g
C) 2.90 × 10−² g
D) 3.44 × 10¹ g
E) 8.97 × 10² g