Holding supply constant, an increase in demand will
a) increase both the quantity and price.
b) increase the equilibrium price and decrease the equilibrium quantity.
c) decrease the equilibrium price and increase the equilibrium quantity.
d) decrease both the quantity and price.

A) increase both the quantity and price.

Explanation:

When demand increases (that is, when the demand curve shifts to the right) and supply remains constant, both the equilibrium price and the quantity increase.

The demand curve is a useful tool for predicting the possible effect of certain economic situations on the frequent consumption of goods and for understanding the qualitative behaviour of markets.

The price demand curve normally has a downward trajectory that shows how, as the price rises, consumption of the product decreases.

When the demand curve shifts to the right, it explains an increase in demand due to the variation of a factor other than price, and when the curve shifts to the left, it shows a decrease in demand also due to the variation of a factor other than price.

Shifts in the demand curve may be due to

   The increase in the population demanding the good.

   Changes in the outlook for future prices.

   Changes in consumer preferences.

   The increase in the disposable income of some consumers.

a progressive tax is a tax that imposes a lower tax rate on low-income earners compared to those with a higher income, making it based on the taxpayer's ability to pay. that means it takes a bigger percentage from high income earners than it does from low income people.