The problem: A thermometer is taken from inside a room to the outside, where the air temperature is 5 degrees Fahrenheit. After one minute, the thermometer reads 55 degrees Fahrenheit, and after 5 minutes it reads 30 degrees Fahrenheit. What is the initial temperature in the room?
I use: T(t)=Tm-ce^kt
but what is my Tm? would it be 5 degrees Fahrenheit? and if so, won't I still have two unknowns: c and k?