CREATE TABLE table_26986076_6 (sat_21_aug VARCHAR(255), tues_24_aug VARCHAR(255))
What was the Sat 21 Aug time for the rider whose Tues 24 Aug time was 20' 38.40 109.680mph?
    
SQL: SELECT sat_21_aug FROM table_26986076_6 WHERE tues_24_aug = "20' 38.40 109.680mph"