12. Of an initial amount of 7000 g of lead-210, how much will remain in 100 years (lead-210 decays at a rate of 3.15%/yr)? round to the nearest tenth. Extra Credit 13. A coroner arrives at a murder scene at 10 p.m. She finds the temperature of the body to be 85.8 F. She waits one hour, takes the temperature again, and finds it to be 83"F. She notes that the room temperature is 72 F. When was the murder committed