One end of a steel wire is fixed to the ceiling of an elevator moving up with an acceleration $2 \ m/s^2$ and a load of $10 \ kg$ hangs from the other end. If the cross-section of the wire is $2 \ cm^2$, then the longitudinal strain in the wire will be ($g = 10 \ m/s^2$ and $Y = 2.0 \times 10^{11} \ N/m^2$).

• A
  $4 \times 10^{-6}$
• B
  $3 \times 10^{-6}$
• C
  $8 \times 10^{-6}$
• D
  $2 \times 10^{-6}$