with respect to bad debts, what is the allowance method?

* Recognizing bad debt expense after confirming that a specific customer is not going to pay

* Including bad debt expense as a subtraction from the sales amount rather than as a separate expense

* Estimating and recognizing bad debt expense in the same period in which the associated sale takes place

* including bad debt expense in the computation of cost of goods sold in the period in which the sale takes place