Solve. -The Function a = A0e-0.01155x Models the Amount in Pounds

Multiple Choice

Solve.
-The function A = A0e-0.01155x 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 300 pounds of the material are placed in the vault, how much time will need to pass for only 53
Pounds to remain?

A) 160 yr
B) 150 yr
C) 155 yr
D) 300 yr