Answer Question 15 (6 points) A scientist begins with 450 grams of a radioactive substance. After 45 minutes, the sample has decayed to 100 grams. Round to the nearest minute, what is the half-life of this substance? Your Answer: Answer Question 16 (6 points) A linen artifact found in a crypt contains 88 percent of the carbon-14 that is present in living flax. To the nearest year, about how many years old is the artifact? (The half- life of carbon-14 is 5730 years.) Your Answer: Answer Question 17 (6 points) A turkey is taken out of the oven with an internal temperature of 200 Fahrenheit and is allowed to cool in a 60 F room. After half-hour, the internal temperature of the turkey is 140 F. To the nearest minute, how long will it take the turkey to cool to 90 F? Your