MAYBE

Problem:
 b(a(b(x1))) -> b(a(a(a(b(x1)))))
 b(a(a(a(b(a(a(b(x1)))))))) -> b(a(a(b(a(a(b(a(a(a(b(b(x1))))))))))))
 b(a(a(a(b(a(a(a(b(x1))))))))) -> b(x1)
 b(a(a(a(b(b(b(x1))))))) -> b(b(b(a(a(a(b(x1)))))))
 b(a(a(b(b(x1))))) -> b(x1)
 b(b(a(a(b(x1))))) -> b(x1)
 b(a(a(a(b(a(b(x1))))))) -> b(x1)
 b(a(b(a(a(a(b(x1))))))) -> b(x1)

Proof:
 Open