d
variation of resistance with temperature

\(16=R_{0}\left[1+\alpha\left(15-T_{0}\right)\right]\)

\(20=R_{0}\left[1+\alpha\left(100-T_{0}\right)\right]\)

Assuming \({T}_{0}=0^{\circ} {C}\), as a general convention.

\(\Rightarrow \frac{16}{20}=\frac{1+\alpha \times 15}{1+\alpha \times 100} \Rightarrow \alpha=0.003^{\circ} {C}^{-1}\)