JAMB Economics 2019 Paper

Concept:Excess demand is the difference between quantity demanded and quantity supplied at a given price.Explanation:First, calculate quantity demanded at ₦18.Substitute $p = 18$ into $Q_d = 7p - 12$:$Q_d = 7(18) - 12 = 126 - 12 = 114$ units.Next, calculate quantity supplied at ₦18.Substitute $p = 18$ into $Q_s = 4p + 9$:$Q_s = 4(18) + 9 = 72 + 9 = 81$ units.Excess demand is found by subtracting quantity supplied from quantity demanded:Excess demand $= Q_d - Q_s = 114 - 81 = 33$ units.Answer:The magnitude of excess demand is $33$ units.Correct option: D.