CREATE TABLE table_2780146_6 (pm__g_kwh_ VARCHAR, co__g_kwh_ VARCHAR)

What's the PM for the standard with 12.3 g/kWh CO?
SELECT pm__g_kwh_ FROM table_2780146_6 WHERE co__g_kwh_ = "12.3"
SELECT "pm__g_kwh_" FROM "table_2780146_6" WHERE "12.3" = "co__g_kwh_"