To determine the correct statement, let's analyze the relationship between the increase in supply and the increase in total receipts of the bidders:
If the total receipts of the bidders increase with each increase in supply, it suggests that the demand for the good is responsive to changes in supply. In other words, as the supply of the good increases, the demand also increases, leading to higher total receipts.
Based on this information, the correct statement is: a) demand is elastic.
In an elastic demand, a change in supply leads to a proportionally larger change in quantity demanded, resulting in a greater change in total receipts.