The only temprature at which the temprature is constant is T=8 celsius,

as that this temprature dT/dt=0. That is unless k=0, which means that

the system is perfectly insulated from its environment (assumed to be at

8 celsius).

The higher k the greater the rate of loss of temprature, the lower k the

lower the rate of loss of temprature, and the rate of heat loss is proportional

to the rate of change of temprature.

So small k - good insulation, high k - poor insulation

RonL