Question: What is the area of this region of Central Europe located mostly in Poland, in which Złotniki Lubańskie was formerly part of the historic Upper Lusatia region at its border?

full_context: Document 1: List of companies of Poland: Poland is a country in Central Europe, situated between the Baltic Sea in the north and two mountain ranges (the Sudetes and Carpathian Mountains) in the south. Bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine and Belarus to the east; and the Baltic Sea, Kaliningrad Oblast (a Russian exclave) and Lithuania to the north. The total area of Poland is 312679 km2 , making it the 69th largest country in the world and the 9th largest in Europe. With a population of over 38.5 million people, Poland is the 34th most populous country in the world, the 8th most populous country in Europe and the sixth most populous member of the European Union. Poland is a unitary state divided into 16 administrative subdivisions, and its capital and largest city is Warsaw. Other metropolises include Kraków, Wrocław, Poznań, Gdańsk and Szczecin.
Document 2: Bad Muskau: Bad Muskau (] ; formerly "Muskau", Upper Sorbian: "Mužakow" , Polish: "Mużaków" ) is a spa town in the historic Upper Lusatia region in Germany at the border with Poland. It is part of the Görlitz district in the State of Saxony.
Document 3: Lower Lusatia: Lower Lusatia (German: "Niederlausitz" , Lower Sorbian: "Dolna Łužyca" , Upper Sorbian: "Delnja Łužica" , Polish: "Łużyce Dolne" , ) is a historical region in Central Europe, stretching from the southeast of the German state of Brandenburg to the southwest of Lubusz Voivodeship in Poland. Like adjacent Upper Lusatia in the south, Lower Lusatia is a settlement area of the West Slavic Sorbs whose endangered Lower Sorbian language is related to Upper Sorbian and Polish.
Document 4: Leśniaki, Będzin County: Leśniaki is a village in the administrative district of Gmina Siewierz, within Będzin County, Silesian Voivodeship, in southern Poland. It lies approximately 6 km north-east of Siewierz, 24 km north-east of Będzin, and 36 km north-east of the regional capital Katowice.
Document 5: Silesia: Silesia ( ; Polish: "Śląsk" ; Czech: "Slezsko" ; German:    ] ; Silesian German: "Schläsing"; Silesian: "Ślůnsk" [ɕlonsk] ; Lower Sorbian: "Šlazyńska" ; Upper Sorbian: "Šleska" ; Latin: "Silesia" ) is a region of Central Europe located mostly in Poland, with small parts in the Czech Republic and Germany. Its area is about 40,000 km2 , and its population about 8,000,000. Silesia is located along the Oder River. It consists of Lower Silesia and Upper Silesia.
Document 6: Landsmannschaft Schlesien: The Landsmannschaft Schlesien - Nieder- und Oberschlesien e.V. ("Territorial Association of Silesia - Lower and Upper Silesia", "Homeland Association of Silesia - Lower and Upper Silesia") is an organization of Germans born in the former Prussian provinces of Lower and Upper Silesia, and their descendants, who currently live in Germany. The Landsmannschaft Schlesien was established in March 1950 and is a member of the Federation of Expellees, and has its headquarters in Königswinter, North Rhine-Westphalia.
Document 7: Ostrava: Ostrava (Polish: "Ostrawa" , German: "Ostrau" or "Mährisch Ostrau") is a city in the north-east of the Czech Republic and is the capital of the Moravian-Silesian Region. It is 15 km from the border with Poland, at the meeting point of four rivers: the Odra, Opava, Ostravice and Lučina. In terms of both population and area Ostrava is the third largest city in the Czech Republic, the second largest city in Moravia, and the largest city in Czech Silesia; it straddles the border of the two historic provinces of Moravia and Silesia. The population was around 300,000 in 2013. The wider conurbation – which also includes the towns of Bohumín, Doubrava, Havířov, Karviná, Orlová, Petřvald and Rychvald – is home to around 500,000 people, making it the largest urban area in the Czech Republic apart from the capital, Prague.
Document 8: Kłodzko Land: Kłodzko Land (Czech: "Kladsko" ; German: "Glatzer Land" ; Polish: "ziemia kłodzka" ) is a historical region in southwestern Poland, which belongs to this country since 1945. Geographically speaking, Kłodzko Land (with an approximate area 1,640 km) consists of the Kłodzko Valley surrounded by parts of the Sudetes mountains, which together forms a significant jut into neighbouring Czech area. The land, named after its capital city of Kłodzko, today forms Kłodzko County of the Lower Silesian Voivodeship.
Document 9: Ruszów, Lower Silesian Voivodeship: Ruszów (German: "Rauscha" ) is a village in the administrative district of Gmina Węgliniec, within Zgorzelec County, Lower Silesian Voivodeship, in south-western Poland. Ruszów is within the historic Upper Lusatia, homeland of Lusatian Sorbs. It lies approximately 13 km north of Węgliniec, 31 km north-east of Zgorzelec, and 133 km west of the regional capital Wrocław.
Document 10: Upper Lusatia: Upper Lusatia (German: "Oberlausitz" ; Upper Sorbian: "Hornja Łužica" ; Lower Sorbian: "Górna Łužyca" ; Polish: "Łużyce Górne" or "Milsko"; ) is a historical region in Germany and Poland. Along with Lower Lusatia to the north, it makes up the region of Lusatia, named after the Slavic "Lusici" tribe. Both Lusatias are home to the West Slavic minority group of the Sorbs.
Document 11: Labe (hamlet): Labe (German: Elbe) is a hamlet in Šumperk District, Olomouc Region, Czech Republic. It was founded by German settlers from Vrchlabí in 1521. Vrchlabí is called "Hohen Elbe" in German language, thus the hamlet is obviously named after settlers' hometown. Czech name is a consequence of bad understanding of name's evolution. Officials believed the name was derived from Elbe River which is called Labe in Czech Language.
Document 12: New Luika Gold Mine: The New Luika Gold Mine is an active mine in the Lupa Gold Field, an area of about 2,600 km2 in south west Tanzania, north of Mbeya, that is known for its gold deposits. It is the principal mine of Shanta Gold and saw its first gold pour in August 2012.
Document 13: Złotniki Lubańskie: Złotniki Lubańskie (German: "Goldentraum" ) is a village in the administrative district of Gmina Leśna, within Lubań County, Lower Silesian Voivodeship, in south-western Poland. Situated on the left bank of the Kwisa river, the settlement was formerly part of the historic Upper Lusatia region at the border with Silesia.
Document 14: Szwajcaria Kaszubska: Szwajcaria Kaszubska ("Kaszëbskô Szwajcariô", Kashubian and German: "Kaschubische Schweiz" ) (literally: "Kashubian Switzerland") - is the northern region of the Kashubian Lake District. In the region of the Kashubian Switzerland is located the highest point in the Polish Lowland ("Niż Polski") - Wieżyca (329 metres above sea level).
Document 15: Slovakia: Slovakia ( ; Slovak: "Slovensko" ] ), officially the Slovak Republic (Slovak: "Slovenská republika" ,    ), is a landlocked country in Central Europe. It is bordered by the Czech Republic and Austria to the west, Poland to the north, Ukraine to the east and Hungary to the south. Slovakia's territory spans about 49000 km2 and is mostly mountainous. The population is over 5 million and comprises mostly ethnic Slovaks. The capital and largest city is Bratislava. The official language is Slovak.
ground_truth: 40,000 km2