对于某一学校超市，其他各单位到其的距离不同，同时各单位人员去超市的频度也不同。请为超市选址，要求实现总体最优。（带权有向图的中心点）-Schools for a supermarket, other units of the distance of its different units while the frequency of the supermarket staff are also different. Please supermarket location, required to