no default constructor found in base class ball

[omniscient232]

i want the class BeginBall to extend Ball, but when i do so, this error shows up.
this is my code:

package
{
    import flash.events.Event;
    import flash.display.MovieClip;
    
    public class Ball extends MovieClip
    {
        public var nSpeedX:Number;
        public var nSpeedY:Number;
        public var ballNr:int;
        const BALLDIAMETER = 10;
        private var nStageWidth:Number = 500;
        private var nStageHeight:Number = 400;
        
        public function Ball ( X,Y,NSpeedX:Number, NSpeedY:Number ) : void
        {
            nSpeedX = NSpeedX;
            nSpeedY = NSpeedY;
            x = X;
            y = Y;
            
            this.addEventListener ( Event.ENTER_FRAME, onEnterFrameHandler );
        }
        
        private function onEnterFrameHandler ( E:Event ) : void
        {
            this.x -= nSpeedX;
            this.y -= nSpeedY;
            
            if ( this.x >= nStageWidth - BALLDIAMETER - 16 )
            {
                this.x = nStageWidth - BALLDIAMETER - 16;
                nSpeedX *= -1;
            }
            else if ( this.x <= BALLDIAMETER + 16 )
            {
                this.x = BALLDIAMETER + 16;
                nSpeedX *= -1;
            }
            
            if ( this.y >= nStageHeight - BALLDIAMETER - 16 )
            {
                this.y = nStageHeight - BALLDIAMETER - 16;
                nSpeedY *= -1;
            }
            else if ( this.y <= BALLDIAMETER + 16 )
            {
                this.y = BALLDIAMETER + 16;
                nSpeedY *= -1;
            }
            
        }
    }//end of class
    
    public class BeginBall extends Ball
    {
        //alles over spatieknop en muisknop etc.
    }
} 

i tried to do public last class Ball, butit says access identifiers are not allowed with namespace attributes.
how can i let BeginBall normally inherit Ball's constructor, or if its not possible, make a new one for BeginBall?