Brass at $\;30^{0}C\;$ is observed to be 1 m long when measured by a steel scale which is connect at $\;0^{0}C\;$ . Correct length of the brass of at $\;0^{0}C\;$ is $\;(\alpha_{steel}=12 \times 10^{-6}/^{0}C\;and \; \alpha_{brass}=18 \times 10^{-6}/^{0}C\;)$