The work done by a woman in 8 hours is equal to the work done by a man in 6 hours and by a boy in 12 hours. If working 6 hours per day 9 men can complete a work in 6 days, then in how many days can 12 men, 12 women and 12 boys together finish the same work, working 8 hours per day? `1 1/2d a y s` b. `3\ d a y s` c. `3 2/3d a y s` d. `4 1/2d a y s`