648                                                     20

,        $100,  $50,  -
    {0, $50 - $100} == 0.     IV,. = 0. -
 ,      $100, ,  $150.   -
     {0, $150 - $100} = $50. , IV,. = , - . 
,         ,   
   :   (   -
    )  ,        45 
 - (   ,  1).    -
       ,     . 20.3(6).

          ,
     .      -
 ,        . ,
    $150,      $40, . .  $10  
  (  $50),     .
        .    -
  $140,   ,       
 $150.         $10   .
       $50,     $150.

20.5.2          

 . 20.3        . 
         , 
   7.    . 20.4,    
 .    ,    -
  $100,      .  -
,        
.       .   
 -   ,  ,     , 
 .

 . 20.4 ()  ()        -
  . . 20.4 ()  ()     -
     .

  . 20.4 ()  ().      -
     ,     (20. la)
 (20.16),   . 20.3,    .  , 
  :

 = IV - . =

=  {0, ^ - \ -  =

=  {-^,  -  - ^ } .                    (20.2)

 = IV -  =
       

=  (,  - } -  =

1    '                    5'              

=  {-,  - , - ^} ,                    (20.2)

 ^          ,  ^   
    .  ,     
       ,  ^,  
     . ,   
          , -
        .