The coefficient of linear expansion of copper is $16.7 \times 10^{-6}$ K$^{-1}$. Its coefficient of volume expansion is —

• a$16.7 \times 10^{-6}$ K$^{-1}$
• b$33.4 \times 10^{-6}$ K$^{-1}$
• c$50.1 \times 10^{-6}$ K$^{-1}$
• d$5.57 \times 10^{-6}$ K$^{-1}$