Step 1: Understanding cost equations.
The cost equations relate the total cost, variable cost, average cost, and output in production. Each equation describes a different aspect of how costs are calculated.
Step 2: Analyzing the options.
(A) Average variable cost = \(\frac{\text{Total variable cost}}{\text{Output}}\): Correct. This is the correct definition of average variable cost. It is the total variable cost divided by the number of units produced.
(B) Total variable cost = Average Variable Cost \(\times\) Quantity: Correct. This equation correctly relates total variable cost to average variable cost and quantity.
(C) Average cost = \(\frac{\text{Total cost}}{q}\): Correct. Average cost is defined as the total cost divided by the number of units produced.
(D) All of these: Correct. All of the equations listed above are valid cost equations.
Step 3: Conclusion.
The correct answer is (D) because all of the equations are correct.