The diameter of the piston of a hydraulic automobile is D metre. What pressure, in atmosphere is required to lift a car of mass m kg?

• A

  $\frac{4\mathrm{mg}}{{\mathrm{\pi D}}^2\times {10}^5}$

• B

  $\frac{2\mathrm{mg}}{{\mathrm{\pi D}}^2}$

• C

  $\frac{\mathrm{mg}}{{\mathrm{\pi D}}^2}$

• D

  ${10}^5\times \frac{4\mathrm{mg}}{{\mathrm{\pi D}}^2}$