4.試分別就短期與長期兩種情況,分析完全競爭市場中生產者之生產均衡條件。(20分)

2. A metal sphere of radius a carries a charge Q. It is surrounded, out to radius b, by linear dielectric material of permittivity . Find the potential at the center (relative to infinity) ,the bound volume charge density, and the bound surface charge density at the inner and outer surfaces, respectively. (20%)