What does Sara offer to do for Becky to make her life a little more bearable? (Chap 5 )

Sara tells Becky that if she comes to her room at the same time each day, she will tell her a story.... in installments.

"You haven't time to hear it now, I'm afraid," she said; "but if you will tell me just what time you come to do my rooms, I will try to be here and tell you a bit of it every day until it is finished. It's a lovely long one—and I'm always putting new bits to it."