Newton's law of cooling help, please!

A murder victim has been shot through the head with a revolver. A suspect is found standing over the victim at 10:15PM holding the revolver. At 10:30PM the coroner records a body temperature of 26°C and it was also recorded that the room temperature was 21°C. An hour later a second reading of the body temperature yielded 24°C. The suspect was seen in public from 6PM to 9PM. Given that the normal body temperature of a living person is 37°C use Newton’s law of cooling to determine whether or not the suspect has an alibi.

If you can, please help!

I'm not able to help you directly but found this website with a very similar problem, might be of some use.

If you enter a value in the box at the bottom and sumbit it gives you a step step by guide to solving it.

BioMath: Newton's Law of Cooling

Hope this helps