<p></p><p>The demand equation is : p+x/100=40</p><p>where p is price and x is quantity demanded.</p><p>(a) Express the demand x as a function of p</p><p>(b) Find the elasticity of demand E(p) by using logarithm differentiation</p><p>(c) What is the elasticity of demand when p=$5? If the price is increased by 10%, what is the approximate change in demand?</p><p>(d) What is the elasticity of demand when p=$15? If the price is increased by 10%, what is the approximate change in demand?</p><p>(e) What is the elasticity of demand when p=$20? If the price is increased by 10%, what is the approximate change in demand?</p><p>我自己算出的结果（b）中弹性是一个常数，这样的话下面3题的答案不全都一样了？所以我不是很确定自己有没有做错，望各位高手帮忙一下</p>