A firm buys on terms of $\frac{2}{20},$ net $40.$ It does not take the discount, and it generally pays after $80$ days. What is the nominal annual percentage cost of its non$-$free trade credit, based on a $365-$day year?

$$ a$.6\mathrm{.}08\%$

b$.15\mathrm{.}21\%$

c$.12\mathrm{.}41\%$

d$.9\mathrm{.}31\%$

e$.2\mathrm{.}04\%$