
## 3.1.1 F Light S

While in the passive mode  ATTac 2000 does not bid in the airline auctions  In active mode ATTac-200 buys all currently unowned airline tickets needed for the current   * In most cases that means that it only bids for airline tickets during its first bidding opportunity in the active mode However in the face of drastically changing hotel and entertainment ticket  prices   * could change sufficiently to necessitate purchasing additional flights  in stead of simply using the ones that have already been purchased

## 3.1.2 Hotels

When in the passive mode ATTac-200 bids in the hotel auctions either to try to win hotels cheaply should the auction close early or to try to prevent the hotel auctions from closing early  It might be advantageous to prevent a hotel auction from closing if no rooms are currently desired in order to keep open the option of switching to that hotel should future market prices warrant it For each hotel room of type such as  Grand Hotel night  "  let be the number of rooms of type   needed for   *   Based on the current price of ATTac-2000 tries to acquire   rooms where

$\begin{array}{cccc}\text{if}&\text{only true at the outset of the game}\\ \text{max}&\text{if}&\le\\ \text{max}&\text{if}&\le\\ \text{max}&\text{if}&\le\\ \end{array}$
If ATTac-2000s outstanding bids would already win   rooms should the auction close at the current price then ATTac-200 does nothing should the auction close prematurely ATTac-200 wins the   rooms cheaply  and competitors lose the opportunity to get any rooms of type later in the game Otherwise ATTac-2000 bids for rooms at $ above the current ask price The formula for computing was selected so as to risk wasting up
$ per room type for the benefit of maintaining flexibility later in the game The to $
exact parameters here were chosen in an ad hoc fashion without detailed experimentation Our intuition is that ATTac-200 s performance is not very sensitive to their exact values In the active mode ATTac-200 bids on hotel rooms based on their marginal value within
* be the value of * the income from all clients minus the cost of allocation the yet to be acquired goods Let * r be the optimal allocation should client fail to get its hotel rooms Note that * 1 might differ from * in the distribution of entertainment tickets as well as in the flights and hotels of client ATTac-200 bids for the hotel rooms assigned to client   in  * at a price of
* -
**
Since at this point flights are a sunk cost  this price tends to be more than $
Notice that ATTac-200 bids the full marginal utility for each hotel room required by the client s travel package An alternative would have been to divide the marginal utility over the number of rooms in the package  which would have eliminated the risk of spending more on hotels than the itinerary is worth On the other hand failing to win a single hotel room is enough to invalidate the entire itinerary ATTac-2000 bids the full marginal utility to maximize the chance that valid itineraries are obtained for all clients In a combinatorial