For the donation of the project 'Awesome Audiobooks Make Avid Readers', what was the percentage of the tip in the total amount?
Awesome Audiobooks Make Avid Readers' is the title; percentage = Divie(donation_optional_support, donation_total)*100;
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'