X234 2-6 0.30.40.3 0.3x=2 0.7x=3 F(x){1 x=4 x< 2 0x>42 - 6 X 2 3 4 P 0.3 0.4 0.3  === = 0 4 0 2 1 4 0.7 3 0.3 2 ( ) xxxxx F x