Answer:
D.  34.00%
Explanation:
The computation of the new contribution margin is shown below:
As we know that 
Contribution Margin = Net Sales Revenue - Variable Expenses
where, 
Net sales revenue is 
= 604 units × $32.5 
= $19,630
The variable expense = Total material cost + total labor cost
Total Material Cost = 604 units × $14.36 = $8,673.44
Total Labor Cost = 604 units × $7.09 = $4,282.36
So, the variable expense is 
= $8,673.44 + $4,282.36 
= $12,955.8
Now 
Contribution margin = $19,630 - $12,955.8 = $6,674.2
And, 
Contribution margin ratio = Contribution margin ÷ net sales
So,  Contribution margin = $6,674.2 ÷ $19,630 
= 34.00%