E(2-E5(-Em) √D√Dn +∞ st (t-ps dtds 2IV1-p2 p +∞ (t- ps) =」a√2兀 p dtds √2z1-p exp 2(1-p2) exp ds=p7             x  x x   =         = −       − − − −         = −       − − − − + − = = − −      + − + − + − + − + − ds s s dtds s s t t s dtds st s t s D D E E E 2 exp 2 2(1 ) ( ) exp 2 2 1 exp 2 2(1 ) ( ) 2 exp 2 1 ( )( ) 2 2 2 2 2 2 2 2 2 2