For a competitive firm, profit per unit of output is equal to a. P - ATC.

The formula to compute profit is:

Totalprofit=Totalrevenue−TotalcostTotalprofit=Totalrevenue−Totalcost

Totalprofit=PriceQuantity−TotalcostQuantityTotalprofit=PriceQuantity−TotalcostQuantity

Therefore, the profit per unit is as follows:

Profitperunit=(PriceQuantity−TotalcostQuantity)÷QuantityProfitperunit=(PriceQuantity−TotalcostQuantity)÷Quantity

Profitperunit=Price−Averagetotalcost