Hi

I've been given the following question;Jane makes coffee with water from an urn which is at a temperature of 95 deg C.It then asks me to find A, B and k. I know my answers for A and B are correct (25 and 70 respectively) but i am struggling to find k.

Jane carries a thermometer with her at all times and notes that 7 minutes later her coffee has cooled to 70 deg C.

The room is not air-conditioned, and is 25 deg C.

Suppose the temperature follows Newton’s Law of Cooling:

where is the number of minutes after the coffee was made.

It does then ask me to find the temperature after 10mins and the time for the coffee to reach 60degrees which i also have correct (62degrees and 11mins respectively). I used a value of k= ln(14/9) but it tells me this is incorrect.

Am i doing something wrong?

Thanks