Step 1: Understanding the Question:
The question asks to identify the best example of a variable cost from the given options. A variable cost is a cost that changes in direct proportion to the level of production or business activity.
Step 2: Analysis of Options:
Let's analyze each option to determine if it is a variable or fixed cost.
(A) Interest on capital: This is generally a fixed cost. The interest payment on borrowed capital (like loans) does not typically change with the volume of production in the short term.
(B) Material cost: The cost of raw materials used in production is a classic example of a variable cost. If a company produces more units, it will need to purchase more raw materials, and the total material cost will increase proportionally.
(C) Wealth tax: This is a tax on an individual's or entity's net worth. It is not related to the level of production and is considered a fixed expense or a non-operating expense.
(D) Rent: Rent for a factory or office space is a fixed cost. The rental amount remains the same each month, regardless of how many units are produced.
Step 3: Final Answer:
Based on the analysis, material cost is the only cost that directly varies with the level of production. Hence, it is the best example of a variable cost.