ƚ  W  .    &  & MathTypeSymbol 0؟ww w- f-2 lw(ySymbol K0؟ww w- f-2 l)ySymbol 0؟ww w- f-2 S(ySymbol L0؟ww w- f-2 )y-@=Symbol 0؟ww w- f-2 l(ySymbol M0؟ww w- f-2 l )ySymbol 0؟ww w- f-2 l (ySymbol N0؟ww w- f-2 l )yk Times New Roman؟ww w- f-2  1y2 n- 2y2 nR2y2 2y2 n1y Times New Roman؟ww w- f-2 2ySymbol ؟ww w- f-2  +y2 -y2 n +y2 n2-y2 `y2 +y2 n+yTimes New Roman؟ww w- f-2  xy2 xy2 n xy2 n6xy2 xy2 nxy & "System- f !-