A and B can do a piece of work in 7 days. With the help of C they finish the work in 5 days. C alone can do that piece of work in? Choose the correct answer.
A) 33
B) 878
C) 30
D) 88
E) 11
30 = 1/5 – 1/6 = 1/30 =&gt; 30 days   Answer: 30
<result>C</result>
A and B can do a piece of work in 7 days. With the help of C they finish the work in 5 days. C alone can do that piece of work in?