Answer:
Total variable cost= $50,600
Step-by-step explanation:
Giving the following information: 
5,000 units:
Direct materials $ 6.60
Direct labor $ 3.65 
Variable manufacturing overhead $ 1.45 
Sales commissions $ 0.50 
Variable administrative expense $ 0.45
Total unitary variable cost= $12.65
Now, for 4,000 units:
Total variable cost= 12.65*4,000 
Total variable cost= $50,600