What do you two talk about?

Prof.Albert Einstein,the great scientist was very unassuming and homely.A 12 year old girl used to drop in on Mr.Einstein on her way home from the school.Her parents were happy but somewhat surprised too.One evening the little girl's mother asked the professor,"What do you teo talk about everyday?"
"Oh", laughed the world famous scientist,"She brings me cookies and i do arithematic for her".