Newton's Law of Cooling states that an object heats or cools at a rate directly proportional to the difference between its current temperature [math]x[/math] and the temperature [math]E[/math] of its environment. [br]That is, [math]\frac{dx}{dt}=b\left(E-x\right)[/math], where [math]t[/math] denotes time and [math]b[/math] is constant.[br]Given a starting temperature of [math]x\left(0\right)[/math], the solution is [math]x\left(t\right)=E+\left(x\left(0\right)-E\right)e^{-bt}[/math].[br]If you know [math]x\left(0\right)[/math], [math]t[/math] and [math]x\left(t\right)[/math], you can solve for [math]b=\frac{-1}{t}\cdot ln\left(\frac{x\left(t\right)-E}{x\left(0\right)-E}\right)[/math].