What was the Sat 21 Aug time for the driver whose Thurs 26 Aug time was 20' 56.01 108.143mph?
create table table_26986076_6 (sat_21_aug varchar, thurs_26_aug varchar, PRIMARY KEY (sat_21_aug))
select sat_21_aug from table_26986076_6 where thurs_26_aug = "20' 56.01 108.143mph"