5. Determine the value of the real parameter $k$ so that the two curves $y = e ^ { x }$, $y = 6 - k e ^ { - x }$ are tangent to each other, finding the coordinates of the point of tangency.
5. Determine the value of the real parameter $k$ so that the two curves $y = e ^ { x }$, $y = 6 - k e ^ { - x }$ are tangent to each other, finding the coordinates of the point of tangency.