The correct answer is A. zero.
The elasticity of supply is a measure of how much the quantity supplied of a good or service changes in response to a change in its price. It is calculated as the percentage change in quantity supplied divided by the percentage change in price.
A supply function is a mathematical relationship that shows how much of a good or service producers are willing and able to supply at different prices. The supply function for a good or service is typically upward-sloping, which means that producers are willing to supply more of a good or service at higher prices.
The supply function of q = 20p is a perfectly inelastic supply function. This means that the quantity supplied does not change at all in response to a change in price. The elasticity of supply for a perfectly inelastic supply function is zero.
Here is a brief explanation of each option:
- Option A: zero. A perfectly inelastic supply function is a supply function where the quantity supplied does not change at all in response to a change in price. The elasticity of supply for a perfectly inelastic supply function is zero.
- Option B: unity. A unitary elastic supply function is a supply function where the percentage change in quantity supplied is equal to the percentage change in price. The elasticity of supply for a unitary elastic supply function is equal to one.
- Option C: more than unity. A supply function with elasticity greater than unity is a supply function where the percentage change in quantity supplied is greater than the percentage change in price. This means that producers are willing to supply more of a good or service in response to a small increase in price.
- Option D: less than unity. A supply function with elasticity less than unity is a supply function where the percentage change in quantity supplied is less than the percentage change in price. This means that producers are willing to supply less of a good or service in response to a small increase in price.