来源:98年北大企管 Q: Toby Talkalot subscribes to a local phone service that changes a fixed fee of $10 per month and allows him to place as many local phone calls as he likes without further charge. Let good 1 be an aggregate of commodities other than local phone use and let good 2 be local phone use. (Measure good 1 on the horizontal axis and good 2 on the vertical axis.) On Monday, Toby didn't use the telephone at all. The slope m of his indifference curve at the consumption bundle he chose on Monday was A)positive B)less than or equal to 0 C)0 D)greater than 0 E)negative 补习班给的答案是A(但另有详解写E) A的解释是由於纵轴的室内电话费率是0 因此Toby面对的预算限制式为垂直线 若他在星期一的最适选择是角解横轴商品 表示此时无异曲线一定是正斜率 选E的详解表示:虽然星期一没有使用~但费用已缴~无论有没有使用电话~都视为已购买 我的想法是:若把电话费率放在纵轴 那他星期一没有使用的确可看做价格下跌至无穷 但为什麽角解横轴一定表示无异曲线是正斜率呢? 有请高手解答了!谢谢!! 有在研究所问题板问过 有板友说Varian的课本有这一题 而答案给C 想请问看看到底要怎麽解释呢? 现在有三个版本啦...QQ ※ 编辑: scodowying 来自: 111.249.192.166 (07/27 00:36)