Three men A, B and C working together can do a job in 6 hours less time then A alone, in 1 hour less time than B alone and in one half the time needed by C when working alone. Then A and B together can do the job in :
[A] $\frac{2}{3}\ hour$
[B] $\frac{3}{4}\ hour$
[C] $\frac{3}{2}\ hour$
[D] $\frac{4}{3}\ hour$