Answer:
 $9,400
Explanation:
For computing the maximum contribution margin we need to do following calculations
Contribution Margin 
Product A = ($12 ÷3) = 4
Product B = ($5 ÷ 1) = 5
Product C = ($9 ÷ 2) = 4.50
So, the ranking order would be product B > product C > product A
Now 
Total machine hours available = 2,100 hours
And, 
Time for making 500 units of B 
= 500 × 1 
= 500 hours
For making 500 units of C, the time taken is  
 = 500 × 2 
= 1000 hours
So the remaining hours left is 
= 2,100 hours - 1,000 hours - 500 hours 
= 600 hours  
So, for A the manufactured is 
= 600 ÷ 3 
= 200
And, finally the Maximum contribution margin  is 
= (200 × $12) + (500 × 5) + (500 × 9)
= $2,400 + $2,500 + $4,500
= $9,400