Answer:
Option (b) is correct.
Explanation:
Initial price of good Y = Total revenue/units sold
= $100/50
= $2
New price of good Y = Total revenue/units sold
= $120/40
= $3
Percentage change in quantity demanded for good X:
[tex]=\frac{current\ quantity-Initial\ quantity}{average\ quantity}\times 100[/tex]
[tex]=\frac{40-20}{30}\times100[/tex]
= 67%
Percentage change in price of good Y:
[tex]=\frac{current\ price-Initial\ price}{average\ price}\times 100[/tex]
[tex]=\frac{3-2}{2.5}\times100[/tex]
= 40%
Therefore,
[tex]Cross\ price\ elasticity=\frac{percentage\ change\ in\ quantity\ demanded\ for\ good\ X}{percentage\ change\ in\ price\ of\ good\ Y}[/tex]
[tex]Cross\ price\ elasticity=\frac{0.67}{0.40}[/tex]
= 1.67
Hence, good X and good Y are substitute goods because as the price of good Y increases as a result demand for good X increases and cross price elasticity is positive. The cross price elasticity is 1.67.