In paragraph 21, what determined which pass they would take?

the amount of food
the amount of gasoline
the photos to be taken
the weight of the plane
the height of the pass

(passage below)

yet how well, after all, could judgment forecast the ultimate result? there were few facts on which we might base a decision. we knew, for example, from amundsen's report that the highest point of the pass of axel heiberg glacier was 10,500 feet. we should know, in a very few minutes, after june had calculated the gasoline consumption, the weight of the plane. from that, we could determine, according to the tables we had worked out and which were then before me, the approximate ceiling we should have. we should know, too, whether or not we should be able to complete the flight, other conditions being favorable.