JIn this feat, Retsu Kaioh pulverizes a wall.
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The volume of said pulverized area was already decided to be that of 536265.4 cc.
In chapter 209, Tokugawa states that the walls are made of concrete reinforced with steel. That's the reason the calc is being redone, the original assumed stone/cement.
Since the walls are made mainly of concrete and are only reinforced with steel, i'll assume 3/4 concrete and 1/4 steel.
3/4 * 536265.4 * 40 = 16087962J
1/4 * 536265.4 * 1000 = 134066350J
134066350 + 16087962 = 150154312J
0.035 tons, 9-A
Retsu has better feats than this anyways.