In a firm's total cost, fixed and variable costs are added together. If Q is given in the expression, you just need to substitute that value for the marginal cost. There is a formula for total cost.

A fixed cost remains constant when production is increased or decreased. Variable costs are a key factor in determining a product's contribution ... You can find a company's variable costs on ...

Fixed costs can be used to calculate key metrics, including a breakeven analysis or a company's operating leverage. Mira Norian / Investopedia Fixed costs don’t change with production levels.

This involves working out the contribution that each product sold provides towards the fixed costs of a business. Firstly, a business must work out the contribution, this is calculated as ...