Newton's Law of Cooling: finding time of death from body temperature

[R_M]

A detective finds a murder victim at 9 AM. The temperature of the body is measured at 90.3-degrees Fahrenheit. One hour later the temperature of the body is 89.0-degrees Fahrenheit. The temperature of the room has been maintained at a constant temperature of 68-degrees Fahrenheit. Estimate the time the murder occurs. I went through the problem and got a time of .229 hours but I'm not sure that number makes sense since shouldn't I be getting a negative number? Please help! Thank you.

 

[R_M]

Nvm everyone. I was able to find my error!