The valuable Bill

One day a little boy came near his mother who was cooking in the kitchen, and gave her a little paper where he had written something. Having dried her hands and taken off her apron, the mother read the little paper:
To mow the grass: $15.00
To clean my bedroom this week: $5.00
To take care of my little brother: $5.00
To go to the bakery: $0.50
To take out the garbage: $2.50
To get good grades: $50.00
To clean the patio: $5.00
TOTAL: $83.00

Having finished reading it, the mother looked at her child seriously, and not saying anything, she took a pencil and started to write on the other side of the paper:
Because I had you in my womb for 9 months and gave you the life: NOTHING
Because of the sleepless nights when I held you and prayed for you: NOTHING
Because of the happyness and love of our family: NOTHING
Because of the fear and worries that I had when you were sick: NOTHING
Because of the food, clothes and education: NOTHING
Because of my help when you needed it: NOTHING

After that, the boy read the paper, looked at his mother's eyes and cried. Then he said: "I love you mom..." And took a pencil and wrote in bigger letters: FULLY PAID!