A can do a piece of work in 4 days. B can do it in 5 days. With the assistance of C they completed the work in 2 days. Find in how many days can C alone do it?	Choose the correct choice:
A) 22 days	B) 20 days	C) 67 days	D) 17 days	E) 18 days
C = 1/2 - 1/4 - 1/5 = 1/20   =&gt; 20 days   Answer:20 days
<result>B</result>
A can do a piece of work in 4 days. B can do it in 5 days. With the assistance of C they completed the work in 2 days. Find in how many days can C alone do it?