Final answer:
The contribution margin does vary with the quantity of items sold, increasing as sales increase. Price floors and ceilings do not shift demand or supply; rather, they create surpluses or shortages by preventing prices from reaching equilibrium levels.
Step-by-step explanation:
The contribution margin does vary depending on the quantity of items sold. The contribution margin is defined as the sales revenue minus the variable costs of producing the product. As more items are sold, the total contribution margin will increase. However, the contribution margin per unit remains constant because it does not include fixed costs, which do not change with the level of output.
On the other hand, for questions regarding market interventions such as price floors and ceilings, it is important to understand their effects on market equilibrium. A price floor, set above equilibrium, does not shift demand or supply but creates a surplus by preventing the price from falling to its equilibrium level. A price ceiling, set below equilibrium, also does not shift demand or supply but creates a shortage by preventing the price from rising to the equilibrium level.