None
Conclusion:
hyp,M,N:Formula List.
q,r:Formula.
a:Assignment.
a |= <hyp, q::(M @ N)>
a |= <hyp, r::(M @ N)>
a |= <hyp, M @ (q
r::N)>
1. a |= <hyp, M @ (q 2. a |= <hyp, q::(M @ N)>
r::N)>
a |= <hyp, r::(M @ N)>