A body of weight $''64 N''$ is pushed with just enough force to start it moving across a horizontal floor and the same force continues to act afterwards. If the coefficients of static and dynamic friction are 0.6 and 0.4 respectively, the acceleration of the body is : (acceleration due to gravity = g)
( A ) $\frac{g}{6.4}$
( B ) $0.64 \; g$
( C ) $0.2 \;g$
( D ) $\frac{g}{32}$