During the month of july, pittsburgh resident b. fly must make four round-trip flights between pittsburgh and

chicago. the dates of the trips are as shown in table 87. b. fly must purchase four round-trip tickets. without a discounted fare, a round-trip ticket between pittsburgh and chicago costs $500. if fly’s stay in a city includes a weekend, then he gets a 20% discount on the round-trip fare. if his stay in a city is at least 21 days, then he receives a 35% discount; and if his stay is more than 10 days, then he receives a 30% discount. of course, only one discount can be applied toward the purchase of any ticket. formulate and solve an assignment problem that minimizes the total cost of purchasing the four round-trip tickets. (hint: let xij 1 if a round-trip ticket is purchased for use on the ith flight out of pittsburgh and the jth flight out of chicago. also think about where fly should buy a ticket if, for example, x21 1.)

leave pittsburg leave chiago
monday, july 1 friday, july 5
tuesday, july 9 thursday, july 11
monday, july 15 friday, july 19
wednesday, july 24 thursday, july 25