How Long Does It Take for 105 Mg of Tritium ${ }_{1}^{3} \mathrm{H}$

How long does it take for 105 mg of tritium, ${ }_{1}^{3} \mathrm{H}$ ,to decay to 35.0 mg? The half-life of tritium is 12.3 yr.

A) 12.3 yr
B) 14.2 yr
C) 19.5 yr
D) 24.6 yr
E) 36.9 yr