NOPAT = EBIT * (1-Tax Rate). If there’s no interest, then EBIT is same thing as EBT…, so the only thing left before you get to Net Income is taxes.
NI = EBIT * (1-Tax Rate)…, if there’s no interest payment.
Therefore, if there’s no interest payment, NOPAT = NI
No interest payment, then NOPAT + Dep = Operating CF
No interest payment, then NI + Dep = Operating CF