Radon ²²²Rn Is a Radioactive Gas Produced as Part of the Natural

Radon ²²²Rn is a radioactive gas produced as part of the natural decay chain of uranium.Because it is a gas,it can pose a health problem through inhalation,especially when high concentrations accumulate in homes.Suppose 5 $\times$ 10⁸ radon atoms are present in a basement at some time.If the basement is sealed and left,then how many radon atoms remain after a month (31 days) ? (The half-life of ²²²Rn is 3.82 days.)

A) 1.81 $\times$ 10⁶
B) 1.49 $\times$ 10⁵
C) 1.23 $\times$ 10⁶
D) 6.16 $\times$ 10⁷
E) None of these is correct.