SELECT "Class" FROM table_78229 WHERE "Prom. (m)" > '30' AND "Peak" = 'sail'
Which Class is Peak Sail when it has a Prom larger than 30?
CREATE TABLE table_78229 (
    "Peak" text,
    "Height (m)" real,
    "Prom. (m)" real,
    "Class" text,
    "Parent" text
)