The average score of the six math tests is a, the average score of the last four times is 3 points higher than a, and the average score of the first, second and sixth times is 3.6 points lower than a, then the average score of the first five times is higher than that of a a How many points have been reduced.
六次数学测验的平均分为a，后四次的平均分比a提高了3分，第一、第二和第六次的平均分比a低了3.6分，那么，前五次平均分比a降低了多少分．
<result>0.24</result>