calculus - newton's law of cooling?

Hi, i have a calculus hw problem which is the following -

Use Newton's Law of Cooling. The coroner arrives at teh scene of a murder at 2AM. he takes the temperature of the body and finds it to be 61.1 degrees . He waits one hour, takes the temperature again, and finds it to be 57.2 degrees . The body is in a meat freezer, where the temperature is 10 degrees . When was the murder comitted?

I was absent when the teacher went over this and i have no clue what to do. can someone please give me a step by step workthrough of the problem, or if thats too hard to type out, tell me what to do, and what the answer should be so i can check it? thanks for any help!

btw, there is no unit given for degrees, but i dont think that should matter.......