Answer:
A 10% change in price causes reduction by 10 units.
Explanation:
Elasticity can be solved by:
Change in quantity demanded / price change
Price change = $(1-0.20)
Change in quantity demanded = 70 - 50 = 20
So elasticity = 20/80 = 0.25
So we have that a 20 percent change in price causes reduction in quantity by 20 units. In line with this, a 10 % rise in price would make quantity to reduce by 10 units.
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