ƚ R e .  &@ & MathTypeSymbol b؟ww w f-2 ":y2 :y2 :y2 =y2 +y2 =y2 +yTimes New Roman؟ww w f-2  8y2 2y2 5y2 1y2 3y2 2yTimes New Roman؟ww w f-2 yy2 xy2 yy2 xy & "System f !-