WAEC Economics 2011 Paper

Concept:A vertical supply curve indicates perfectly inelastic supply, where quantity supplied does not change when price changes.Explanation:Elasticity of supply measures how responsive quantity supplied is to a change in price.The coefficient is calculated as:$E_s = \frac{\% \text{ change in quantity supplied}}{\% \text{ change in price}}$When the supply curve is vertical, quantity supplied is fixed at every price.So, any change in price causes zero change in quantity supplied.Therefore, the percentage change in quantity supplied is $0\%$.This gives:$E_s = \frac{0}{\text{positive percentage change in price}} = 0$Thus, vertical supply has an elasticity coefficient of zero.Answer:A. $0.0$