$A$ steel plate of face area $1 \, cm^2$ and thickness $4 \, cm$ is fixed rigidly at the lower surface. $A$ tangential force $F = 10 \, kN$ is applied on the upper surface as shown in the figure. The lateral displacement $x$ of the upper surface with respect to the lower surface is .............. $m$ (Modulus of rigidity for steel is $8 \times 10^{11} \, N/m^2$).

• A
  $5 \times 10^{-5}$
• B
  $5 \times 10^{-6}$
• C
  $2.5 \times 10^{-3}$
• D
  $2.5 \times 10^{-4}$