To determine the correct answer, we need to analyze how changes in demand and supply affect the equilibrium price. Let’s break down each scenario:

Solution By Steps

Step 1: Demand Increases and Supply Does Not Change

When demand increases and supply remains constant, the quantity demanded exceeds the quantity supplied at the current price. This leads to a shortage, which pushes the price up until equilibrium is reached. Therefore, the equilibrium price increases.

Step 2: Demand Does Not Change and Supply Decreases

If demand stays the same but supply decreases, there is less of the good available at the current price. This creates a shortage, leading to higher prices as consumers bid up the price to secure the limited supply. Thus, the equilibrium price increases.

Step 3: Demand Increases and Supply Decreases Simultaneously

When both demand increases and supply decreases, the effect on price is compounded. The higher demand and lower supply both contribute to a higher equilibrium price, as the shortage becomes more pronounced.

Final Answer

The correct answer is: increases and supply does not change, when demand does not change and supply decreases, and when demand increases and supply decreases simultaneously.