Question: Which elevation groundstation has a capacity in persons/hour larger than 820, and a Name or route of lager 1, and a slope length smaller than 336?
SQL: SELECT AVG("elevation groundstation") FROM "2-17814458-1" WHERE "capacity in persons/hour" > 820.0 AND "Name or route" = 'lager 1' AND "slope length" < 336.0;

Question: Which slope length has a type of surface lift, and an elevation groundstation smaller than 1974, and a construction year(s) of 1971, and a Name or route of Alpmatten 1?
SQL: SELECT "slope length" FROM "2-17814458-1" WHERE "type" = 'surface lift' AND "elevation groundstation" < 1974.0 AND "construction year(s)" = '1971' AND "Name or route" = 'Alpmatten 1';