Answer:
c.8,250 hours 
Step-by-step explanation:
The computation is shown below:
= (Fixed expenses + target profit) ÷ (Contribution margin per unit) 
where, 
Contribution margin per unit = Selling price per unit - Variable expense per unit 
= $35 - $21
= $14 
Now the number of hours to achieve the target income is 
= ($78,000 + $37,500) ÷ ($14)
= 8,250 hours 
We simply applied the above formula