1 | 10. B: T List 11. u = u1 & v v1 @ B [u / v] v1 @ B A',B':T List. [u / v] = (A' @ B') & A' [u1 / v1] & B' B | 6 steps |
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2 | 10. B: T List 11. A',B':T List. [u / v] = (A' @ B') & A' [u1 / v1] & B' B u = u1 & v v1 @ B [u / v] v1 @ B | 8 steps |