co.combinatorics – Find a function that respect these 3 conditions


I am working on this problem about a way to calculate revision needed when memorizing a text by heart and I didn’t found how to solve this 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
    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.
  2. b” is a variable starting at “c” and incrementing by 1 at each revision until reaching “d“.

If the question is too difficult, I could define a, c and d and also give the function f