Solve the Problem $5.1 \times 10 ^ { 8 } \mathrm { yr }$

Multiple Choice

Solve the problem.
-The half-life of an element is $5.1 \times 10 ^ { 8 } \mathrm { yr }$ . How long does it take a sample of the element to decay to $\frac { 2 } { 5 }$ of its original mass? (Express results in scientific notation, rounded to the nearest hundredth.)

A) $5.80 \times 10 ^ { 8 } \mathrm { yr }$
B) $6.74 \times 10 ^ { 8 } \mathrm { yr }$
C) $1.14 \times 10 ^ { 8 } \mathrm { yr }$
D) $3.24 \times 10 ^ { 8 } \mathrm { yr }$