There are three principal layers; 1  External intercostal muscles aid in quiet and forced inhalation. They originate on ribs 1-11 and have their insertion on ribs 2-12. 2  Internal intercostal muscles aid in forced expiration (quiet expiration is a passive process).
Costs. A professional concrete contractor will typically charge $2-$4 per square foot for a simple stain application, including the sealer. A stain application with patterning and sawed lines will typically cost between $4 and $10 per square foot.
Economical. The cost of concrete floors is very low, about $2 to $6 per square foot to polish a plain gray slab, giving it a lustrous sheen. The concrete's tonal differences, subtle cracks and aggregates take on a stonelike, natural feel.he cost of concrete floors is very low, about $2 to $6 per square foot to polish a plain gray slab, giving it a lustrous sheen. The concrete's tonal differences, subtle cracks and aggregates take on a stonelike, natural feel.