Answer:
Martinez Company
1. Total amount of product costs for 10,000 units:
= 10,000 * $13.90 
= $139,000
2. Period costs for 10,000 units:
= 10,000 * $6.15 
= $61,500
3. Variable cost per unit of 8,000 produced and sold:
= $11.55
4. Variable cost per unit of 12,500 produced and sold:
= $11.55
5. Total variable costs for 8,000 units produced and sold:
= 8,000 * $11.55
= $92,400
6. Total variable costs for 12,500 units produced and sold:
= 12,500 * $11.55
= $144,375
7. Average fixed manufacturing cost per unit produced for 8,000 units:
= $4.00
8. Average fixed manufacturing cost per unit produced for 12,500 units:
= $4.00
9. Total fixed manufacturing cost for 8,000 units:
= 8,000 x $4.00
= $32,000
10. Total fixed manufacturing cost for 12,500 units:
= 12,500 x $4.00
= $50,000
11. Total amount of manufacturing overhead costs for 8,000 units:
= 8,000 * $5.60
= $44,800
per unit = $5.60
Variable manufacturing overhead = $1.60
Fixed manufacturing overhead =     $4.00
Total per unit =                                  $5.60
12. Total amount of manufacturing overhead for 12,500 units:
= 12,500 x $5.60
= $70,000
per unit = $5.60
Variable manufacturing overhead = $1.60
Fixed manufacturing overhead =     $4.00
Total per unit =                                  $5.60
13. Contribution margin per unit:
Selling price =                                          $21.40
Variable manufacturing cost per unit =  $9.90
Contribution margin per unit                  $11.50
14. Total amounts of direct and indirect manufacturing costs for 12,000 units:
Direct manufacturing costs = $9.90 x 12,000 =   $118,800
Indirect manufacturing costs = $4.00 x 12,000 = $48,000
15. Incremental manufacturing cost if Martinez increases production from 10,000 to 10,001:
= $9.90
Explanation:
a) Data and Calculations:
Average Cost Per Unit
Direct materials                              $ 5.40
Direct labor                                     $ 2.90
Variable manufacturing overhead $ 1.60
Total Variable Costs per unit        $ 9.90
Fixed manufacturing overhead    $ 4.00
Total product cost per unit          $13.90
Period Costs:
Fixed selling expense                   $ 2.40
Fixed administrative expense       $ 2.10
Sales commissions                         $ 1.10
Variable administrative expense $ 0.55
Total period costs  per unit           $6.15
All Variable costs:
Variable production costs             $9.90
Sales Commission                           $1.10
Variable administrative expense $ 0.55
Total Variable costs                      $11.55
All Fixed Costs:
Fixed manufacturing overhead    $ 4.00
Fixed selling expense                   $ 2.40
Fixed administrative expense       $ 2.10
Total fixed costs per unit               $8.50