Answer
$0.23\frac{K}{s}$
Work Step by Step
We know that
$\frac{\Delta T}{\Delta t}=\frac{45^{\circ}F-(-4.0^{\circ}F)}{2.0 min}$
$\frac{\Delta T}{\Delta t}=24.5\frac{F^{\circ}}{min}$
Now we can convert this rate of change of temperature in Kelvin as
$(24.5\frac{F^{\circ}}{min})(\frac{1min}{60s})(\frac{1K}{1.8}F^{\circ})=0.23\frac{K}{s}$
