Answer:
U-shaped
Explanation:
Since the marginal product of labor is decreasing, the average variable costs and marginal costs will be increasing at all points, but the average fixed costs will be decreasing. That is why the average total costs (which includes both variable and fixed costs per unit) will be U-shaped since they will fall at the beginning when the decrease in marginal product of labor is small, bu then will increase as the marginal product of labor falls even more.