Answer: desirable mix of output.
Explanation:
It should be noted that spending of consumers will rise when there's an healthy economy and growth in stock market. This implies that more goods are been bought by the people are therefore there'll be more demand for goods.
When inflation rate is at zero, it simply bmeans that there's no robust economy and the demand for goods is not competitive. Therefore, changes in relative prices signal a change in the desirable mix of output.