A and B can finish a work in 16 days while A alone can do the same work in 20 days. In how many days B alone will complete the work?
Choose the correct choice from the following options
A) 76 days  B) 48 days  C) 80 days  D) 31 days  E) 22 days

Rationale: "b = 1 / 16 – 1 / 20 = 1 / 80 = > 80 days answer : c"
Answer: C