static IVector multiplyVectorByNumber(IVector a, double number) {

        double vx = a.getVx() * number;
        double vy = a.getVy() * number;

        if(a instanceof Vector3D) {
            double vz = ((Vector3D) a).getVz() * number;
            return new Vector3D(vx, vy, vz);
        }
        return new Vector(vx, vy);
    }