Consider two parallel tilt boundaries with misorientations $\_1$ and $\_2.$ Show that, thermodynamically, we would expect the two boundaries to join and form one boundary with misorientation $\_1+$ $\_2.$

Note; This question is taken from Chapter $5$ of the textbook, "Mechanical Behavior of Materials" $(2$nd Edition$)$ by Meyers and Chawla. A textbook solution can be found but PLEASE DO NOT COPY THIS SOLUTION! The solution does not make any sense and doesn't explain WHY the solution is done the way it is$.$ Please provide as much explanation as possible. Thanks!