CREATE TABLE table_57018 ("Date" TEXT, "Course" TEXT, "Distance" TEXT, "Type" TEXT, "Winner" TEXT)

What type has rest day as a course and was on 21 may?
SELECT "Type" FROM table_57018 WHERE "Course" = 'rest day' AND "Date" = '21 may'
SELECT "Type" FROM "table_57018" WHERE "Course" = 'rest day' AND "Date" = '21 may'