There is a circular lawn with a circumference of 94.2 meters, and it is planned to install an automatic rotary sprinkler device for irrigation. There are three devices with a range of 20 meters, 15 meters and 10 meters. Which one do you think is more suitable? Where is it installed?
有一个周长94.2米的圆形草坪，准备为它安装自动旋转喷灌装置进行喷灌．现有射程为20米、15米、10米的三种装置，你认为选哪种比较合适？安装在什么地方？
<gadget id="calculator">94.2 / 3.14 / 2</gadget>
<output>15</output>

<result>15</result>