How Long Would It Take $4.00 \times 10 ^ { 20 }$

Multiple Choice

How long would it take $4.00 \times 10 ^ { 20 }$ atoms to decay to $1.00 \times 10 ^ { 19 }$ atoms if their half-life was $14.7$ years?

A) 147 years
B) $58.8$ years
C) $78.2$ years
D) $29.4$ years