A and B can finish a work in 12 days while A alone can do the same work in 20 days. In how many days B alone will complete the work? Pick one:  A) 76 days  B) 30 days  C) 98 days  D) 31 days  E) 22 days

Rationale: "b = 1 / 12 – 1 / 20 = 2 / 60 = 1 / 30 = > 30 days answer : b"
Answer: B