A body starts from rest and travels a distance x with uniform acceleration then it travels a distance 2x with uniform speed, finally it travels a distance 3x with uniform retardation and comes to rest.If the complete motion of particle is along a straight line,then the ratio of its average velocity to maximum velocity during its motion is -
a )( 2 / 5 ) b )( 3 / 5 ) c )( 4 / 5 ) d ) (6 / 7 )