I have come through an error in Kaplan notes for economics book 2 page 42 Q no 12 on elasticity the answer 3600 does not confirm to the concept Please help
You are correct that is a mistake. 3,600 is the value of the Quantity Demanded of air conditioners at the given price and income levels. To find the income elasticity, differentiate the equation given with respect to income, giving:
dQD / dIncome = .0004.
To find elasticity, multiply this by (Income / QD), giving:
(dQD / dIncome) * (Income / QD) = .0004 * (4,000,000 / 3,600) = 0.44.