Final answer:
Jane used the win-lose negotiation tactic called lowballing, by adding an additional $5,000 charge after the initial agreement on the computer system.
Step-by-step explanation:
In the scenario described, Jane used a win-lose negotiation tactic known as lowballing. Lowballing happens when one negotiating party initially agrees on a certain price or set of terms but then adds additional charges after the agreement is thought to have been finalized. In this case, after finalizing the negotiation for the new computer system, Jane added an unexpected $5,000 installation and instruction charge, which is an example of this tactic. It's intended to catch the other party off-guard, hoping that they will agree to the additional charge after having already committed to the purchase.