Capital budgeting question

Incremental net after-tax cash flows --> Ct = (Rt - OCt) (1-tc) + Dt

Net operating income/earnings --> (Rt - OCt - Dt) (1-tc)

• Rt = operating revenues in time t

• OCt = operating costs in time t

• (Rt- OCt - Dt)tc = taxes paid in time t

• Dt = depreciation expense in time t

• Tc = effective corporate tax rate

how are these two different? And when do I use them?