Database: donor
Question: For the donation of the project 'Awesome Audiobooks Make Avid Readers', what was the percentage of the tip in the total amount?
SQL: SELECT CAST(SUM(T2.donation_optional_support) AS REAL) * 100 / SUM(T2.donation_total) FROM essays AS T1 INNER JOIN donations AS T2 ON T1.projectid = T2.projectid WHERE T1.title LIKE 'Awesome Audiobooks Make Avid Readers'