For the health and safety of the children, the experimental kindergarten provides each child with a water cup. Each cup is 3 yuan, 10% off in Ansheng Supermarket, and "buy 8 get 1 free" in Xinhuadu Supermarket. Kindergarten wants to buy 180 water cups, please be a "consultant", and calculate which one is more cost-effective to buy? Please write your reason.
为了孩子的卫生安全，实验幼儿园给每个小朋友配一个水杯．每只水杯3元，安盛超市打九折，新华都超市"买八送一"．幼儿园想买180只水杯，请你当"参谋"，算一算到哪家购买较合算？请写出你的理由．
<result>180</result>