Asked before but going by info given did not come up with one of my choice answers.?

How long will it take a sample of radioactive substance to decay to half of its original amount,if it decays according to the function At=450e^-0.249t; where t is the time in years. Round to nearest hundredth year. Choices are: 2.78 years, 112.05yrs, 24.54 yrs or 27.32 yrs. Please help. I am praying for istance. Thank you