"Little girls knickers" joke

one day a girl was walking home from school when she ran into a teenager he said to her that if she climbed over the fence and then back over again he would give her $5 so she did. later on after she went home she showed her mum the money
mum: where did you get that from
girl: a boy told me that if i climbed the fence hed give it to me so i did
mum: oh u silly child he just wants to look at your knickers.
The nxt day the girl walked the same way home and the boy told her again except for $10 dollars so she did.
later on when she got home her mum asked her where she got it from she replied
girl: the boy told me that if i climbed the fence he would give me $10 so i did
mum: oh you foolish child he just want to see your knickers girl!
the next day this happened again but for $20 the girl went home to show her mum and her mum said
" on you silly girl i have told you time and time again that he just wants to see your knickers, when will you learn??
girl: but mummy i did learn, i wasnt wearing any!!! 11