A vehicle is moving with a velocity v on a curved road of width b and radius of curvature R . For counteracting the centrifugal force on the vehicle the difference in elevation required in between the outer and inner edges of the road is

• A

  $\frac{{\mathrm{v}}^2\mathrm{b}}{\mathrm{Rg}}$

• B

  $\frac{\mathrm{rb}}{\mathrm{Rg}}$

• C

  $\frac{{\mathrm{vb}}^2}{\mathrm{Rg}}$

• D

  $\frac{\mathrm{vb}}{{\mathrm{R}}^2\mathrm{g}}$