A can have a piece of work done in 10 days, B can work two times faster than the A, C can work three times faster than A. How many days will they take to do the work together ? Choose the correct choice from the following choices:
A) 3/5 days
B) 5/2 days
C) 4/3 days
D) can't say
E) none
A's 1 day work is 1/15   5/2 days's 1 day work is 2/15   C's 1 day work is 3/15   (A+5/2 days+C)'s 1 day work(1/15+2/15+3/15) is 2/5   so, they can finish the work in 5/2 days   ANSWER:5/2 days
<result>B</result>
A can have a piece of work done in 10 days, B can work two times faster than the A, C can work three times faster than A. How many days will they take to do the work together ?