Answer:
B's share of Day's losses = 25% x $73,000 = $18,250
B's basis in Day = $10,000 - $18,250 = $0, because a basis cannot be negative.
Since a S corporation is a pass through entity, it is not taxed directly, instead its shareholders are taxed. In this case, B can deduct $10,000 in losses in year 1. Since the losses cannot exceed B's basis, there is nothing else B can deduct in year 2.