Answer:
                                                 Regular     Low Carb      Total
a) Units to be produced               20              22             42
(to minimize total production cost)
b) Total production costs    $704,000   $1,150,000   $1,854,000
Explanation:
a) Data and Calculations:
                                                 Regular     Low Carb
Monthly customers demand         10              15
Ratio of customers demand        40%           60%
Cost per unit                           $32,000      $50,000
Revenue per unit                    120,000      300,000
Contribution per unit            $88,000    $250,000
Total required revenue = $9,000,000
With 20 additional units of beer, total units produced = 45 (25 + 20)
To minimize production costs and generate a total revenue of $9,000,000, more of the units that cost less should be produced.  Units should be produced according to the following ratio: 
                                                    Regular       Low Carb       Total
New Production and Sales units  20                   22             42
                                          
Total production cost =       $640,000         $1,100,000         $1,740,000
                                        ($32,000 * 20)       ($50,000 * 22)
Total revenue =               $2,400,000        $6,600,000     $9,000,000
                                       ($120,000 * 20)      ($300,000 * 22)
To achieve a minimum revenue of $9,500,000,
New production units                  22                   23                  45
Total production cost =     $704,000         $1,150,000        $1,854,000
Total revenue =                2,640,000         6,900,000         9,540,000