ƚ  PV e .   &`  & MathType-Times New Roman؟ww w f-2 ` xy2 `xyTimes New Roman؟ww w f-2 ` 122 622 n122 `622 322 n222 `462Symbol- ؟ww w f-2 ` =22 `22 `-22 `*2 & "Systemʟ f !-