The length of a steel rod is 10 m at 20°C. If the length becomes 10.0167 m at 120°C, the coefficient of linear expansion of steel is —

• a$1.67 \times 10^{-3}$ °C$^{-1}$
• b$1.67 \times 10^{-4}$ °C$^{-1}$
• c$1.67 \times 10^{-5}$ °C$^{-1}$
• d$1.67 \times 10^{-6}$ °C$^{-1}$