Hansel and gretel, a married couple, manage apartments and they are required to live in the managers' apartment as a condition of their employment. instead of providing the apartment to hansel and gretel rent-free, the owner of the apartment building gives hansel and gretel a housing allowance of $600, which they use to pay rent on the managers' apartment. hansel and gretel pay $600 per month in rent. if they did not live in the managers' apartment, hansel and gretel could live in another apartment building where they would only pay $500 in rent. what amount, if any, must be included in hansel and gretel's gross income?

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.