<p class="MsoNormal" align="left" style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none;"><span lang="EN-US" style="; FONT-FAMILY: "T11","sans-serif"; mso-bidi-font-family: T11; mso-font-kerning: 0pt;">8.4 </span><span lang="EN-US" style="; FONT-FAMILY: "T10","sans-serif"; mso-bidi-font-family: T10; mso-font-kerning: 0pt;">Ernest's income elasticity of demand for natural gas is 0.4. His price elasticity of demand for</span><span style="; FONT-FAMILY: 宋体; mso-bidi-font-family: T10; mso-font-kerning: 0pt; mso-ascii-font-family: T10; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: T10;">　</span><span lang="EN-US" style="; FONT-FAMILY: "T10","sans-serif"; mso-bidi-font-family: T10; mso-font-kerning: 0pt;">natural gas is -</span><span lang="EN-US" style="; FONT-FAMILY: "Arial","sans-serif"; mso-font-kerning: 0pt;">0.</span><span lang="EN-US" style="; FONT-FAMILY: "T5","sans-serif"; mso-bidi-font-family: T5; mso-font-kerning: 0pt;">3</span><span style="; FONT-FAMILY: 宋体; mso-bidi-font-family: T9; mso-font-kerning: 0pt; mso-ascii-font-family: T9; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: T9;">，</span><span lang="EN-US" style="; FONT-FAMILY: "T10","sans-serif"; mso-bidi-font-family: T10; mso-font-kerning: 0pt;">and he spends 10% of his income on natural gas. What is his substitution price</span><span style="; FONT-FAMILY: 宋体; mso-bidi-font-family: T10; mso-font-kerning: 0pt; mso-ascii-font-family: T10; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: T10;">　</span><span lang="EN-US" style="; FONT-FAMILY: "T10","sans-serif"; mso-bidi-font-family: T10; mso-font-kerning: 0pt;">elasticity?<p></p></span></p><p></p><p></p><p class="MsoNormal" align="left" style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none;"><span lang="EN-US" style="; FONT-FAMILY: "T6","sans-serif"; mso-bidi-font-family: T6; mso-font-kerning: 0pt;">(a) </span><span lang="EN-US" style="; FONT-FAMILY: "Arial","sans-serif"; mso-font-kerning: 0pt;">-0.</span><span lang="EN-US" style="; FONT-FAMILY: "T5","sans-serif"; mso-bidi-font-family: T5; mso-font-kerning: 0pt;">26<p></p></span></p><p></p><p></p><p class="MsoNormal" align="left" style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none;"><span lang="EN-US" style="; FONT-FAMILY: "T6","sans-serif"; mso-bidi-font-family: T6; mso-font-kerning: 0pt;">(b) </span><span lang="EN-US" style="; FONT-FAMILY: "Arial","sans-serif"; mso-font-kerning: 0pt;">-0.</span><span lang="EN-US" style="; FONT-FAMILY: "T5","sans-serif"; mso-bidi-font-family: T5; mso-font-kerning: 0pt;">34<p></p></span></p><p></p><p></p><p class="MsoNormal" align="left" style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none;"><span lang="EN-US" style="; FONT-FAMILY: "T6","sans-serif"; mso-bidi-font-family: T6; mso-font-kerning: 0pt;">(c) </span><span lang="EN-US" style="; FONT-FAMILY: "T5","sans-serif"; mso-bidi-font-family: T5; mso-font-kerning: 0pt;">.20<p></p></span></p><p></p><p></p><p class="MsoNormal" align="left" style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none;"><span lang="EN-US" style="; FONT-FAMILY: "T6","sans-serif"; mso-bidi-font-family: T6; mso-font-kerning: 0pt;">(d) </span><span lang="EN-US" style="; FONT-FAMILY: "Arial","sans-serif"; mso-font-kerning: 0pt;">-0.</span><span lang="EN-US" style="; FONT-FAMILY: "T5","sans-serif"; mso-bidi-font-family: T5; mso-font-kerning: 0pt;">12<p></p></span></p><p></p><p></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US" style="; FONT-FAMILY: "T6","sans-serif"; mso-bidi-font-family: T6; mso-font-kerning: 0pt;">(e) </span><span lang="EN-US" style="; FONT-FAMILY: "T5","sans-serif"; mso-bidi-font-family: T5; mso-font-kerning: 0pt;">None of the above.</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US" style="; FONT-FAMILY: "T5","sans-serif"; mso-bidi-font-family: T5; mso-font-kerning: 0pt;"></span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US" style="; FONT-FAMILY: "T5","sans-serif"; mso-bidi-font-family: T5; mso-font-kerning: 0pt;">答案上选A。请教这道题的思路。谢谢。</span></p>

[此贴子已经被作者于2007-12-19 19:48:41编辑过]