Answer the questions based on information in the Washington Post article Oil Prices Have Nosedived. Why Aren't Airfares Doing the Same? The term fuel hedging refers to signing contracts to pay the same price for fuel for a certain period of time. continually upgrading the airline's fleet to the most efficient planes available. adjusting in‑flight procedures to reduce fuel consumption. buying stockpiles of fuel when the price is low.

Because of the violent nature of the sport, professional american football players are at risk of suffering concussions (or brain injuries) during the violent collisions that occur between players during the game. violent collisions involving hits to the head are particularly risky. suppose the commissioner of the national football league (nfl) institutes a rule requiring players to wear a new, lighter helmet that is designed to reduce head trauma during collisions between players on the field. while the new helmets the probability of a concussion resulting from each individual collision, at the same time the new helmets could also give football players an incentive to play more , which could potentially the amount of violent collisions and thus the number of concussions suffered by nfl players, all else equal.