Building:Black Market

The Black Market is a building that allows you to buy and sell military units for gold or other resources.
 * The building has 25 levels and allows the sale of land and sea units for any resources.
 * A requirement for the building is the new "Soldier Exchange" research and a building ground.
 * The building levels unlock the unit types that can be sold, after one another.
 * For every unit type there is a minimum and maximum price, to avoid overpricing or dumping prices.
 * For every soldier exchange, one part of the sale price has to be deducted as tax. With increasing Black Market level, taxes are reduced.
 * The offered troops can be viewed and accepted by other players in the new "Soldier Exchange" tab at their Trading Posts. You can also purchase troops that you haven't researched yourself yet.
 * No Black Market is required to buy troops. Soldier Exchange also does not need to have been researched for purchasing. __NOWYSIWYG__

Description
Our battle-tested warriors in their shiny armour, and our progressive war machines have become legendary. Now it's time to make a profit from them. Other leaders will be eager to purchase these troops. __NOWYSIWYG__

Black Market Information
Black Market is used to offer military units for sale, and be paid with a resource of player's choice! To do so, it is needed to unlock the new research topic "Soldier Exchange" in the Economy section.

This building claims to offer a good cooperation opportunity, since this is a new way to dismiss units without destroying them. Players can create up to eight sale offers, alliance players can have up to twelve; the proceeds from the unit sales are taxed. However, the tax rate is reduced with every Black Market upgrade.

If player has troops in the black market, and town gets attacked, the troops in the black market will join the battle. In this case, they will be removed and player receives a message in the town advisor; as soon as the battle is over offers will be restored and player will receive another message about how many offers could be restored. If player wins the battle, but only XX% of the previously-for-sale troops have survived, then the offers that can be restored, will be restored, with the highest amount possible (latest offers first). __NOWYSIWYG__

Expansion Details
The time (in seconds) it takes to upgrade to the next level is determined by the following formula: $${ \text{Building time (seconds)} = \left \lbrack 4,321 \times 1.1 ^ \text{Level} - 4,627 \right \rbrack }$$

The accumulative time (in seconds) it takes to upgrade up to the next level is determined by the following formula: $${ \text{Accumulative building time (seconds)} = \left \lbrack 47,531 \times \left (\ 1.1 ^ \text{Level} -\ 1\ \right )\ - 4,627 \times \text{Level}\ \right \rbrack}$$

Building:Black Market/1-10|1 - 10 Building:Black Market/11-20|11 - 20 Building:Black Market/21-25|21 - 25 __NOWYSIWYG__