I try to solve this question, but I can't get the clue. Could you give me a guide or direction to solve this?

Careful readers might complain that our analysis of songs like "n Bot- tles of Beer on the Wall" or "The n Days of Christmas" is overly sim- plistic, because larger numbers take longer to sing than shorter num- bers. More generally, because there are only so many words of a given length, larger sets of words necessarily contain longer words. We can more accurately estimate singing time by counting the number of syl- lables sung, rather than the number of words. (a) How long does it take to sing the integer n? (b) How long does it take to sing "n Bottles of Beer on the Wall"? (c) How long does it take to sing "The n Days of Christmas"? As usual, express your answers in the form O(f(n)) for some function f