Trade credit discount. Compute the approximate annual interest cost of not taking a discount using the following scenarios. What conclusion can be drawn from the calculations?

Equation: Approximate interest rate $=[($Discount $\%)/(1-$ Discount $\%)]*[(365/($# of days until payment is due $$ last day for discount$))]$

a$.2/15$ net $20.$

$(0\mathrm{.}02)/(1-0\mathrm{.}02)(365/(20-15))=1\mathrm{.}49=149\%$

b$.2/15$ net $30.$

$(0\mathrm{.}02)/(1-0\mathrm{.}02)(365/(30-15))=0\mathrm{.}50=50\%$

c$.2/15$ net $40.$

$(0\mathrm{.}02)/(1-0\mathrm{.}02)(365/(40-15))=0\mathrm{.}30=30\%$

d$.2/15$ net $50.$

$(0\mathrm{.}02)/(1-0\mathrm{.}02)(365/(50-15))=0\mathrm{.}21=21\%$

e$.2/15$ net $60.$

$(0\mathrm{.}02)/(1-0\mathrm{.}02)(365/(60-15))=0\mathrm{.}17=17\%$