Can you explain answer of these questions? I cannot find out how to get this

 Question 28 (Answer A)

Lazar Industries produces two products, Crates and Boxes. Per unit selling prices, costs. and resource utilization for these products are as follows.

                                          Crates.      Boxes

Selling price.                   $20            $30

Direct material costs.      5                 5

Direct labor costs.            8               10

Variable overhead costs  3                5

Variable selling costs.     1               2

Machine hours per unit.   2              4

Production of Crates and Boxes involves joint processes and use of the same facilities. The total fixed factory overhead cost is S2,000,000 and total fixed selling and administrative costs are $840,000. Production and sales are scheduled for 500,000 units of Crates and 700.000 units of Boxes. Lazar maintains no direct materials, work-in- process, or finished goods inventory. Lazar can reduce direct material costs for Crates by 50% per unit, with no change in direct labor costs. However, it would increase machine-hour production time by 1-1/2  hours unit. For Crates, variable overhead costs are allocated based on machine hours. per What would be the effect on the total contribution margin if this change was implemented?

A. $125,000 increase

B. $250,000 decrease

C.$300,000 increase

D.$1,250,000 increase

Question 20 (Answer C)

Recent economic conditions are forcing MegaCorp to drop its price from $ 50 to $ 40 per unit, but the company expects its sales to rise from 600,000 to  750,000 units.  The company's current variable cost per unit is $ 38.  Suppose MegaCorp would like to maintain a 16% target contribution margin on its sales revenue.  To achieve this target, the company must lower its variable production costs by:

A. $ 2.00 per unit. 

B.$ 33.60 per unit. 

C. $ 4.40 per unit. 

D. $ 6.40 per unit.