Question

We have 0.25 kg of a liquid with a heat capacity of 50 J/K.
We also have a heat source at 15 W which increases the temperature of the liquid until the temperature becomes constant. The heat source is then turned of and the temperature of the liquid starts to decrease at a rate of 1.2 K / min.
Find the Specific heat capacity.

Answer 1

What I've tried:
E_1 = 0.25 * c * 1.2 = 0.3 * c
E_2 = P * t = 15 W * 60 s = 900 J

E_1 = E_2
0.3 * c = 900
c = 3000 J / kg K

But the answer is 2800 J / kg K