Renu can do a piece of work in 5 days, but with the help of her friend Suma , she can do it in 4 days. In what time Suma can do it alone?	Options
A) 10 B) 12 C) 14 D) 15 E) 20

Rationale: "renu â € ™ s one day â € ™ s work = 1 / 5 suma â € ™ s one day â € ™ s work = 1 / 4 - 1 / 5 = 1 / 20 suma can do it alone in 20 days . answer : e"
Answer: E