A firm offers terms of $\frac{1}{25},$ net $40.$

a$.$ What effective annual interest rate does the firm earn when a customer does not take

the discount? $($Do not round intermediate calculations and enter your answer as a

percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$

b$.$ What effective annual interest rate does the firm earn if the discount is changed to $2$

percent? $($Do not round intermediate calculations and enter your answer as a

percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$

c$.$ What effective annual interest rate does the firm earn if the credit period is increased

to $60$ days? $($Do not round intermediate calculations and enter your answer as a

percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$

d$.$ What effective annual interest rate does the firm earn if the discount period is

increased to $30$ days? $($Do not round intermediate calculations and enter your

answer as a percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$