A horizontal force is applied on a body on a rough horizontal surface produces an acceleration ‘a’. If coefficient of friction between the body and surface which is $\mathrm{\mu }$ is reduced to $\mathrm{\mu }$ /3, the acceleration increases by 2 units. The value of ‘ $\mathrm{\mu }$ ’ is

• A

  2/3g

• B

  3/2g

• C

  3/g

• D

  1/g