Asheet of skeletal muscle extends across the ribcage and lies at the base of the thorax. it separates the thoracic cavity from the abdominal cavity. this muscle is the

Sheet of interior skeletal muscle that reaches out over the base of the rib cage. It isolates the thoracic cavity which contain heart, lungs and ribs, from the abdominal cavity.

This also plays out an imperative role in breathing: as it contracts, the volume of the thoracic cavity boosts and air is drawn into the lungs

replace   c   with   a   and simplify.

a = c , b = a, q = n , 2 , a = c , 900 b= a , 700 , q = n , 600 , 2 = b o t h , b = a , q = n