Table: tennessee_cruiser
Columns: name
country
displacement_tons
armament
weight_of_discharge
speed

Question: How much Displacement (tons) has an Armament of 2 x -inch (mm), 16 x -inch (mm)?
SQL: SELECT COUNT("displacement_tons") FROM tennessee_cruiser WHERE "armament" = '2 x -inch (mm), 16 x -inch (mm)'