假设每生产1吨钢要消耗1.5吨煤炭和1.5吨铁矿石，下图中甲、乙两地和乙、丙两地相距都为10 km，甲、丙两地相距8 km。每吨煤炭、铁矿石和钢材的运费分别为0.2元/千米、0.12元/千米和0.35元/千米。据此回答问题。
Tomorrow is Saturday. It will be fine. Sam will play football. Amy will play the piano and Jim will fly kites. Kate will visit her grandma. On Sunday the weather will be sunny. Sam，Amy，Kate and Jim will have a picnic. They are going to take some food and some toys.
李娜是首位在“法网”夺冠的亚洲网球选手，关于李娜发球过程的叙述正确的是（ ）
,点
为圆心的圆弧
上运动,设 
,则
的最大值为( )