Ssa(=LM(-f+M(+f) [o(f+10250)+(f-10250 元4 +[S(f+9750)+(f-9750) 4 +[o(f+12000)+(f-12000) 2 4 [(f+8000)+S(f-8000]26 [ ( ) ( )] 2 1 ( ) DSB c c S f = M f − f + M f + f [ ( 10250) ( 10250)] 2 = f + + f − A    [ ( 9750) ( 9750)] 2 + f + + f − A    [ ( 12000) ( 12000)] 2 + f + + f − A    [ ( 8000) ( 8000)] 2 + f + + f − A   