A City's Water Supply Is Contaminated with a Toxin at a Concentration

A city's water supply is contaminated with a toxin at a concentration of 0.63 mg/L. Fortunately, this toxin decomposes to a safe mixture of products by first-order kinetics with a rate constant of 0.27 day^-1. How long will it take for half of the toxin to decompose

A) 0.17 days
B) 0.27 days
C) 0.38 days
D) 2.3 days
E) 2.6 days