Table: palatine_locomotives_railbuses
Columns: class
railway_number_s
quantity
year_s_of_manufacture
axle_arrangement_uic

Question: what is the quantity when the year of manufacture is 1900 and the class is mc?
SQL: SELECT "quantity" FROM palatine_locomotives_railbuses WHERE "year_s_of_manufacture" = '1900' AND "class" = 'mc'

Question: what is the class when the quantity is 4?
SQL: SELECT "class" FROM palatine_locomotives_railbuses WHERE "quantity" = 4