“…With either choice we would realize three transplants if all vertices and edges are viable and otherwise, no transplant is realized. It is easy to see, however, that there is an advantage to the choice (3,6,4) if we consider the possibility of falling back to (3,4) as follows: if (3,6,4) succeeds, then 3 transplants are realized; if (3,6,4) fails but (3,4) succeeds, then the 2 transplants in (3,4) are realized; if both (3,6,4) and (3,4) fail, then no transplant is realized. Here (3,4) serves as a fallback.…”