Need help figuring out what formula to use to estimate a time of death for a school project?

Body found at 11:55 am
Body temperature 97.5°F at 12:00 pm
97.366°F at 12:30 pm
Air Conditioning set at a constant temperature of 70°F

http://people.uncw.edu/lugo/MCP/DIFF...h/img00001.gif (1)

Newton's Law of Cooling states that the rate of cooling of an object is proportional to the temperature difference between the object and its surroundings, provided that this difference is not too large.1 When estimating the time of death, one needs to know the temperature of the surroundings and the temperature of the body at two different times in order to make an accurate estimate.
It is assumed that the temperature of the body T(t) is governed by Newton's Law of Cooling,
http://people.uncw.edu/lugo/MCP/DIFF...h/img00001.gif (1)
where k is a negative constant, http://people.uncw.edu/lugo/MCP/DIFF...h/img00002.gif is the ambient temperature, and time t is the number of hours since the time of death. Also, the temperature of a human body at the time of death is considered to be 98.6 F, T(0) = 98.6 .