Assuming no other variable costs, the marginal cost of a taco is; $5
Formula for marginal cost is;
Marginal cost = change in cost/change in quantity
We are told the cost of hiring an additional worker is $200.
Thus; change in production cost = $200
We are told that the marginal productivity is 40 tacos. This marginal productivity of the change is cost is the change in quantity.
Thus;
Change in quantity = 40
Finally,
marginal cost = $200/40
Marginal cost = $5
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