ƚ PR P .  &@d & MathType- -5-5"lTSymbol ؟ww w f-2 6(yTSymbolM ؟ww w f-2 )ySymbol ؟ww w f-2 (ySymbolM ؟ww w f-2 S)yTimes New Roman؟ww w f-2 _4y 2 _ 2 _@ 2 2  Times New Roman؟ww w f-2 W2 2 2 Symbol ؟ww w f-2 _= 2 s- 2 = Times New Roman؟ww w f-2 _lx 2 x & "System f !-