A can do a piece of work in 8 days. B can do it in 16 days. With the assistance of C they completed the work in 4 days. Find in how many days can C alone do it? Pick one:
A) 87 days B) 20 days C) 26 days D) 19 days E) 16 days

Rationale: "c = 1 / 4 - 1 / 8 - 1 / 16 = 1 / 16 = > 16 days answer : e"
Answer: E