How many regions had rainfall infiltration (km 3/year) of 9.3?
CREATE TABLE table_28220 (
    "Region" text,
    "Land area (km 2 )" text,
    "Rainfall by depth (mm/year)" real,
    "Rainfall by volume (km 3 /year)" text,
    "Surface run off (km 3 /year)" text,
    "Infiltration (km 3 /year)" text,
    "Evapotranspiration (km 3 /year)" text
)
SELECT COUNT("Rainfall by depth (mm/year)") FROM table_28220 WHERE "Infiltration (km 3 /year)" = '9.3'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: How many regions had rainfall infiltration (km 3/year) of 9.3? ### Input: CREATE TABLE table_28220 (
    "Region" text,
    "Land area (km 2 )" text,
    "Rainfall by depth (mm/year)" real,
    "Rainfall by volume (km 3 /year)" text,
    "Surface run off (km 3 /year)" text,
    "Infiltration (km 3 /year)" text,
    "Evapotranspiration (km 3 /year)" text
) ### Response: SELECT COUNT("Rainfall by depth (mm/year)") FROM table_28220 WHERE "Infiltration (km 3 /year)" = '9.3'