This is how marginal cost and diminishing marginal returns work with the marginal cost taken into account. In a competitive market, the Marginal Cost will determine the Marginal Revenue. In a monopoly market, the demand and supply determine the Marginal Revenue. Marginal Revenue Formula . Marginal Revenue is easy to calculate.

Best diesel fuel additive duramaxMarginal Profit: The extra profit from producing one more item. These marginal values can be found by finding the rate of change of the corresponding function at the current production amount. Example 4: Suppose the daily cost, in dollars, of producing T Lego X-Wing kits is given by the function ( T)=0.002 T3+0.1 T2+42 T+300, and currently ...

I think I have the method you're looking for. You have a cost function for x units given by: C = 10,000 + 5x + (1/9)x^2 Now, the cost per unit is going to be that same function divided by x. Let's call this function U: U = 10,000/x + 5 + (1/9)x To find the minimum total cost, you need to find the minimum of this function.