$($Trade credit discounts$)$ Determine the effective annualized cost of forgoing the trade credit discount on the following terms:

a$.\frac{2}{6},$ net $30$

b$.\frac{2}{7},$ net $45$

c$.\frac{1}{8},$ net $25$

d$.\frac{5}{9},$ net $80$

e$.\frac{5}{7},$ net $70$

f$.\frac{3}{7},$ net $60$