Question: Seiersberg is a former municipality in the Austrian state that has what area?

full_context: Document 1: FH Joanneum: FH Joanneum is one of the largest Universities of Applied Sciences in Austria. It has about 4,000 students and about 578 employees. The main campus is located in Graz, while there are two other locations in Kapfenberg and Bad Gleichenberg. All three are situated in the province of Styria, Austria.
Document 2: Tyrnau: Tyrnau is a former municipality in the district of Graz-Umgebung in the Austrian state of Styria. Since the 2015 Styria municipal structural reform, it is part of the municipality Fladnitz an der Teichalm, in the Weiz District.
Document 3: Styria: Styria (German: Steiermark , ] , Slovene/Croatian: "Štajerska" , Hungarian: "Stájerország" , ) is a state or "Bundesland", located in the southeast of Austria. In area it is the second largest of the nine Austrian federated states, covering 16401 km2 . It borders Slovenia and the Austrian states of Upper Austria, Lower Austria, Salzburg, Burgenland, and Carinthia. The population (as of ) was . The capital city is Graz which had 276,526 inhabitants at the beginning of 2015.
Document 4: Salzburg: Salzburg (] ; Bavarian: "Såizburg" ; literally: "Salt Fortress") is the fourth-largest city in Austria and the capital of the federal state of Salzburg.
Document 5: Linz: Linz ( ; ] ; Czech: "Linec" ) is the third-largest city of Austria and capital of the state of Upper Austria (German: "Oberösterreich" ). It is in the north centre of Austria, approximately 30 km south of the Czech border, on both sides of the River Danube. The population of the city is , and that of the Greater Linz conurbation is about 271,000.
Document 6: Bavaria: Bavaria ( German: "Bayern" ] ; Czech: "Bavorsko" ), officially the Free State of Bavaria (German: "Freistaat Bayern" ] ) is a landlocked federal state of Germany, occupying its southeastern corner. With an area of 70,550.19 square kilometres (27,200 sq mi), Bavaria is the largest German state by land area. Its territory comprises roughly a fifth of the total land area of Germany. With 12.9 million inhabitants, it is Germany's second-most-populous state (after North Rhine-Westphalia). Bavaria's capital and largest city, Munich, is the third largest city in Germany.
Document 7: Eisenstadt: Eisenstadt (] ; Hungarian: "Kismarton" , Croatian: "Željezni grad" , "Željezno" , Slovene: "Železno" ) is a city in Austria, the state capital of Burgenland. It has a population of about 14,241 (2016).
Document 8: Seiersberg: Seiersberg is a former municipality in the district of Graz-Umgebung in the Austrian state of Styria. Since the 2015 Styria municipal structural reform, it is part of the municipality Seiersberg-Pirka.
Document 9: Sankt Lorenzen bei Knittelfeld: Sankt Lorenzen bei Knittelfeld is a former municipality in the district of Murtal in Styria, Austria. Since the 2015 Styria municipal structural reform, it is part of the municipality Sankt Margarethen bei Knittelfeld.
Document 10: Pichl-Kainisch: Pichl-Kainisch is a former municipality in the Salzkammergut in the Liezen (district) Austrian state of Styria. Since the 2015 Styria municipal structural reform, it is part of the municipality Bad Mitterndorf.
Document 11: Geography of Bratislava: Bratislava, the capital city of Slovakia, is situated in Central Europe and it is located in the extreme south-west within Slovakia. The city borders Austria in the west and Hungary in the south making it the only national capital in the world to border two foreign countries. State border with the Czech Republic is only 62 kilometres (38.5 mi) distant. Bratislava lies on the foothills of the Little Carpathians mountains and the city straddles both banks of the Danube River. The city has a total area of 367.58 square kilometres (141.9 mi²), making it the second largest city in Slovakia by area (after the township of Vysoké Tatry). Geomorphologically the city covers the southern tip of the Záhorie Lowland, the entire range of the Devín Carpathians, small westernmost part of the Pezinok Carpahians and the northern tip of the Danubian Lowland.
Document 12: Zerlach: Zerlach is a former municipality in the district of Südoststeiermark in the Austrian state of Styria. Since the 2015 Styria municipal structural reform, it is part of the municipality Kirchbach-Zerlach.
Document 13: Spielfeld: Spielfeld (Slovene: "Špilje") is a former municipality in the district of Leibnitz in Austrian state of Styria. Since the 2015 Styria municipal structural reform, it is part of the municipality Straß in Steiermark. It was an Austria-Slovenia border crossing checkpoint until December 21 2007, when all immigration and customs checks ended after Slovenia joined the Schengen Area. The Slovene town opposite Spielfeld is Šentilj.
Document 14: Sankt Martin am Grimming: Sankt Martin am Grimming is a former municipality in the judicial district of Schladming in the Austrian state of Styria. In 2015 it merged with the municipality of Mitterberg to form the municipality of Mitterberg-St Martin.
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: 16401 km2