Let B be the benefit, Ck be the capital cost and Cr be the recurring cost.Ck is normally much larger than any instant of Cr. Cost/benefit analysis can use which of following formulae?

a. B / (Ck + Cr)

b. (B + Cr) / Ck.

c. Either so long as you remember that (B - Cr) / Ck > B / (Ck + Cr)

d. Either so long as you remember that (B - Cr) / Ck < B / (Ck + Cr)