Which of the following provisions represents the cost principle that governs whether an indirect cost incurred by a nonfederal entity is chargeable or assignable to a Federal grant award using direct labor, square footage, or another allocation base to distribute those costs to Federal grants?

a$.$

$2$ CFR $200\mathrm{.}403$ Allowable costs

b$.$

$2$ CFR $200\mathrm{.}404$ Reasonable costs

c$.$

$2$ CFR $200\mathrm{.}405$ Allocable costs

d$.$

$2$ CFR $200\mathrm{.}406$ Applicable credits