Income elasticity is computed by the formula

A. $${e_i} = \frac{{{Q_1} - {Q_2}}}{{{P_1}}}$$

B. $${e_i} = \frac{{{Q_2} - {Q_1}}}{{\frac{{{Q_1}}}{{\frac{{{Y_2} - {Y_1}}}{{{Y_1}}}}}}}$$

C. $${e_i} = \frac{{{Q_2} - {Q_1}}}{{{Q_1}}} \times \frac{{{Y_1}}}{{{Y_2} - {Y_1}}} \times 100$$

D. $${e_i} = \frac{{{Y_1} - {Q_1}}}{{{Y_2} - {Q_2}}}$$

Answer: Option B