If a crab and a half weigh a pound and a half, but the half crab weights half as much again as the whole crab, what do half the whole crab and the whole of the half crab weigh?

If a crab and a half weigh a pound and a half, but the half crab weights half as much again as the whole crab, what do half the whole crab and the whole of the half crab weigh?