Answer:
 C. $4.20
Step-by-step explanation:
 The computation is shown below:
Before that we need to do following calculations
Total costs to be incurred is 
= ($2 × 5,000,000 units) + $9,000,000 
= $19,000,000 
 Now 
Required return is 
 = $40,000,000 × 5% 
= $2,000,000 
 So, 
Sales price per unit is 
= (Total cost incurred + required return) ÷ number of unit sold 
 = ($19,000,000 + 2,000,000) ÷ 5,000,000 units 
= $4.20