A scientist models the decay of a radioactive substance using the equation , where is the mass in grams after hours, and is the initial mass. Which of the following statements is true?
The substance decays completely in 10 hours.
The mass of the substance decreases by 15% every 10 hours.
The initial mass of the substance is 0.85 grams.
The substance has a half-life of 10 hours.
