Why is it Mrs. Kuriatin readily agrees to have Dolly and Ben come after school to Mitya's party?

Mrs. Kuriatin's son, Mitya, happens to be having a party following school the day Frank stops by. Her complete willingness to have Dolly and Ben come to her home for the event shows the acceptance Frank enjoys within the Russian business community. Frank is regarded not only as a customer, but also as a friend. They are delighted to oblige him with this small favor.