How should you use operating costs when calculating incremental cash flows ?

How should you use operating costs when calculating incremental cash flows?

A. Subtract operating costs, calculate taxes off of that number, and then add them back.

B. Do not subtract operating costs, and then subtract taxes on operating income before operating costs.

C. Subtract operating costs.

D. Subtract taxes as though operating costs were not tax-deductible. Then subtract operating costs.