Answer :
A decrease in people's income would lead to a reduction in demand for solar panels, which would cause lower wages and less employment for solar panel installers.
The scenario that would result in a decrease in the wage rate of solar panel installers and a decrease in the quantity of solar panel installers employed would be the one involving a decrease in people's income, which decreases the demand for solar panels. According to economic principles, as seen in Panel (b) of 'Changes in the Demand for and Supply of Labor', a decrease in labor demand leads to both lower wages and less employment in the affected market.
Therefore, if people in Billy's town have less income, they are less likely to invest in solar panels, reducing the demand for installations and consequently reducing the need for installers, which in turn decreases the wage rate and quantity of solar panel installers employed in Billy's town.
