What do you understand by the own-price elasticity of demand for a good?

supplied to one of its determinants. The law of demand implies that an increase in a price of a good will subsequently lead to a fall in the quantity demanded for that good. The formulae which calculates this amount is the division of the percentage of change in quantity demanded by the percentage of change in price. The sign of price elasticity of demand, and elasticity as well, is always going to be negative due to the fact that quantity and price demanded are usually in opposite directions. Elasticity is going to be negative as well since neither the percentage change in price nor the the percentage change in quantity are going to be positive according to which one will rise or fall. Despite that, elasticity will be treated always as a positive  figure in order to avoid inconvience when dealing with price elasticity of demand. There are five different ranges of variance of price elasticity of demand and the first one occurs when demand is elastic. This is happening when the value of the price of elasticity of demand is positive and the percentage change in quantity is larger than the percentage change in price. This is an indication of demand responding to the change of the price of a ceratin good. The second range occurs when demand is inelastic. This happens when the PED value is less than one and the percentage change in quantity demanded is smaller than the percentage change in price. This shows that demand does not respond to the change of the price of a good. The third range occurs when demand is unit elastic. This happens when the PED is equal to one and the percentage of the change in quantity demanded is equal to the percentage of the change in price. This indicates that demand remains the same whatever the price. The fourth range happens when demand is perfectly elastic. When that occurs PED is equal to infinity and a slight price change leads to an infinite demand of quantity. The fifth range is when demand is perfectly inelastic and the value of PED equals zero. This occurs when the percentage change in price equals zero. There are differentiations in those values of elasticity of demand according to certain determinants which affect the price elasticity of demand. Demand for common goods, goods with very close substitutes, has a tendancy to be more elastic as it is simpler for a customer to be "unfaithfull" with a specific product and choose another one, a slightly different one. Necessity products tend to have inelastic demands whereas luxury  products have elastic demands. Also the boundaries that any market has drew are crucial on the elasticity of demand in that market. Narrowly defined markets, where it is easier to find close substitutes for narrowly defined goods, tend to be more elastic than broadly defined markets. Over a long time period goods tend to have a more elastic demand. Before proceeding to (b) we must clarify that on a linear demand curve the elasticity of demand has many variances amongst the different points on the demand curve and that is why we often refer to some sections of the demand curve between the prices. Usually, in that type of graph, although the slope of the linear demand curve is constant, the elasticity is not. This is explained by the fact that the slope is the ratio of changes in the two variables, while elasticity is the ratio of percentage changes in the two variables. Finally, as for (c) it is necessary to note the fact that business travelling and business accomodation are goods consumpted jointly. That is very common, usually with professionals who travel often and need a residence, which happens to be a rented, hotel residence. Despite that, the terrorist attacks and the subsequent repurcusion this had in economy as a whole brought a downfall in business travelling. The hotels in order to manage this crisis effectively reduced their prices and offered discounts in order to increase the quantity of customers visiting them. If we consider the law of demand in this case, hotel reservations should increase in this period as well as the total revenue of the business but this would happen when the price elasticity of demand is elastic. This happens when the percentage change in quantity is larger than the percentage change in price. Concluding, we would easily say that it is assume that the hotels would increase their total revenue with discounts and better prices but this is not always the case. There are other factors influencing customer behaviour after these terrorist attacks that would not be easily predicted or affluenced.