Final answer:
Cost curves in economics generally have distinct shapes: fixed costs are shown as a horizontal line, variable costs have an upward-sloping curve, marginal costs have a U-shaped curve, and both average total costs and average variable costs usually have U-shaped curves due to efficiency gains and rising variable costs.
Step-by-step explanation:
Shapes of Cost Curves-
When discussing cost curves, it is generally expected that each type has a distinct shape. Fixed costs are typically represented by a horizontal line since fixed costs do not change with the level of output. Variable costs have an upward-sloping curve, reflecting the fact that variable costs increase with output.
Margin cost curves are generally U-shaped, initially decreasing due to increasing marginal returns and then increasing as diminishing marginal returns set in. Both average total costs and average variable costs tend to be U-shaped for similar reasons: they decrease at first due to spreading fixed costs over more units and increasing efficiencies, then eventually increase as the efficiency gains are overshadowed by rising variable costs.
These economic concepts help in understanding how costs change with production levels and are essential for businesses when making production and pricing decisions.