T AS≡ 0-s18 ∮ T QR  =  B A R I T Q ( ) +  A B R II T Q ( ) =0  B A R I T Q ( ) -  B A R II T Q ( ) =0  B A R I T Q ( ) =  B A R II T Q ( ) ΔS≡ B A R I T Q ( ) =  B A R II T Q ( ) =  B A dS