Solve
-The Function $\mathrm { A } = \mathrm { A } _ { 0 } \mathrm { e } ^ { - 0.0077 \mathrm { x } }$

Multiple Choice

Solve.
-The function $\mathrm { A } = \mathrm { A } _ { 0 } \mathrm { e } ^ { - 0.0077 \mathrm { x } }$ models the amount in pounds of a particular radioactive material stored in a concrete vault, where $x$ is the number of years since the material was put into the vault. If 400 pounds of the material are placed in the vault, how much time will need to pass for only 317 pounds to remain?

A) 30 years
B) 35 years
C) 40 years
D) 60 years