Milk World Ltd. is a government-owned milk distribution center. Earlier they used to distribute milk in bottles as shown in the figure for Rs. 8 per bottle. Now they have decided to reduce the price per bottle by 50 paise, by reducing the size of the bottle, However, they do not want their old customers to notice this change in the size of the bottle, so they plan to reduce the circumference of the opening of the bottle without changing the height of the bottle. What is the new circumference of the opening?