I am developing a mobile app to help to memorize by heart and revise a book and I don't know how to solve this math problem.
I have a function f which is a quadratic function representing the total number of memorized lines up to now (so f ' is the number of new memorized lines for the day).
I'm looking for function g which is the number of lines to be revised per day knowing that

1. the book have "l" lines
2. 
   
   1. first, each new line memorized must be revised every day for "a" days
   2. then (after "a" days), the line must be revised once every "b" days.
3. "b" is a variable starting at "c" and incrementing by 1 at each revision until reaching "d".
4. Solve this math problem
5.