Solve the Problem $\mathrm { f } ( \mathrm { x } ) = 600 ( 0.5 ) ^ { \mathrm { x } / 80 }$

Solve the problem.
-The function $\mathrm { f } ( \mathrm { x } ) = 600 ( 0.5 ) ^ { \mathrm { x } / 80 }$ 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. Find the amount of radioactive material in the vault after 140 years. Round to the nearest whole number.

A) 404 pounds
B) 178 pounds
C) 171 pounds
D) 525 pounds