A can do a piece of work in 6 hours; B and C together can do it in 4 hours, which A and C together can do it in 3 hours. How long will B alone take to do it?  Choose one:
A) 8hours
B) 6hours
C) 14hours
D) 12hours
E) 5hours
A's 1 hour work = 1/6;   (B + C)'s 1 hour work = 1/4;   (A + C)'s 1 hour work = 1/3   (A + B + C)'s 1 hour work = (1/4 + 1/6) = 5/12   B's 1 hour work = (5/12 - 1/3) = 1/12   B alone will take 12 hours to do the work.   Answer:12hours
<result>D</result>
A can do a piece of work in 6 hours; B and C together can do it in 4 hours, which A and C together can do it in 3 hours. How long will B alone take to do it?