本研究以Hotelling之線形城市模型為基礎模型，但對運輸成本由消費者負擔之假設改為由生產者負擔，廠商以運送貨物至消費者所在地之形式負擔運輸成本，而非直接補貼消費者之運輸成本。在此新的模型架構之下，本研究對廠商是否能夠向消費者價格歧視，以及是否有買賣承諾存在，兩者組合產生之四種情況分別進行探討。最後得出在廠商不能夠對消費者價格歧視，但無買賣承諾存在時，以及在廠商能對消費者價格歧視，無論買賣承諾存在與否時，兩廠商會設廠於線形城市之1/4及3/4處，達到社會福利極大之均衡。但若廠商不得採價格歧視，而有買賣承諾之存在時，兩廠商會選擇極小化差異，也就是設廠於線形城市之中心點，此時將造成社會的無謂損失。 / This research is based on Hotelling model. The only difference is that the firms have to pay transportation cost in this research. The firms absorb transportation cost in two ways. One way is the firms accept orders from the consumer and send the commodities to them. The other ways is the firms sent the commodities to some chain stores and the consumers will go to buy them in their neighborhoods. Since the transportation cost is decreased almost to zero and thus can be neglected, it is just like the consumers do not have pay it. This research considers four conditions under this new structure -whether the firms can price discriminate or not and whether there exists a commitment between the consumers and firms- combined together. If the firms can price discriminates, the firms will settle down on the 1/4 and 3/4 of the linear city. But if the firms cannot price discriminates, when the commitment exits, they will still choose their location on 1/4 and 3/4, or they will minimize differenciation.