<image>As shown in the figure, the area of square $$OABC$$ is $$4$$, and the hyperbolic function $$y=\dfrac{k}{x}(x > 0)$$ passes through point $$B$$. 

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$$(1)$$ Find the coordinates of point $$B$$ and the value of $$k$$; _ 
$$(2)$$ Fold the square along lines $$AB$$ and $$BC$$ to obtain squares $$AMC′B$$ and $$CBA′N$$ respectively. Let line segments $$MC′$$ and $$NA’$$ intersect the curve $$y=\dfrac{k}{x}$$_$$(k > 0)$$ at points $$E$$ and $$F$$, respectively. Find the equation of the line $$EF$$.