* @param amount сумма сделки.
*/
public void makePlayerBuyLand(Player p, ILand land, int amount) {
ILandOwner owner = land.owner();
if (owner instanceof ILandSeller) {
ILandSeller seller = (ILandSeller) owner;
if (p.buyLand(seller, amount, land)) {
GameModelEvent event = new GameModelEvent(this, land, seller, p);
fireLandChangedOwner(event);