CREATE TABLE table_5062 ("Race" TEXT, "Length" TEXT, "Class" TEXT, "Circuit" TEXT, "Date" TEXT)

Name the length for all class and date of march 18
SELECT "Length" FROM table_5062 WHERE "Class" = 'all' AND "Date" = 'march 18'
SELECT "Length" FROM "table_5062" WHERE "Class" = 'all' AND "Date" = 'march 18'