A clock pendulum made of invar has a period of 0.5sec at 20°C. If the clock is used in a climate where the temperature averages to 30°C, how much time does the clock loose in each oscillation. For invar $\mathrm{\alpha }=9\times {10}^{-70}{\mathrm{C}}^{-1}$

• A

  $2.25\times {10}^{-6}\sec$

• B

  $2.5\times {10}^{-7}\sec$

• C

  $5\times {10}^{-7}\sec$

• D

  $1.125\times {10}^{-6}\sec$