A can do a piece of work in 4 hours; B and C together can do it in 3 hours, while A and C together can do it in 3 hours. How long will B alone take to do it? Choose the correct choice:	A) 12	B) 9	C) 8	D) 6	E) 4
A's 1 hour's work = 1/4 ;   (B + C)'s 1 hour's work = 1/3 ;   (A + C)'s 1 hour's work = 1/3.   (A + B + C)'s 1 hour's work = ( 1/4 + 1/3 ) =7/12 .   B's 1 hour's work = ( 7/12 - 1/3) = 1/4.   Therefore A alone will take 4 hours to do the work.   4
<result>E</result>
A can do a piece of work in 4 hours; B and C together can do it in 3 hours, while A and C together can do it in 3 hours. How long will B alone take to do it?