$3.$ The tax$-$shield approach to calculating operating cash flow $($OCF$)$:

$1.$Treats the corporate income tax deductions arising from depreciation and amortization expenses and the interest charge separately from the after$-$tax operating profit.

$2.$Gives a different value for OCF compared to the usual methods.

$3.$None of the other choices are correct.

$4.$Uses the statutory tax rate to compute the value of the interest tax shield.

$5.$Lumps together sales $($net of all expenses$)$ then applies the effective tax rate to the resulting net profit.

Please explain in detail, thanks!