A piece of material has cross-sectional area $A$ and length $L$. The temperatures on the two faces of the sample are $T_1$ and $T_2$. Thermal energy $Q$ passes through the sample in time $t$. These quantities obey $\frac{Q}{t} = k \times A \times \frac{(T_1 - T_2)}{L}$, where $k$ is a constant. Determine the SI base units of $k$.
- A$\text{kg m s}^{-3}\,\text{^{\circ}C}^{-1}$
- B$\text{kg m s}^{-3}\,\text{K}^{-1}$
- C$\text{kg m s}^{-1}\,\text{^{\circ}C}^{-1}$
- D$\text{kg m s}^{-1}\,\text{K}^{-1}$