Answer:
10 M
Step-by-step explanation:
In case of titration , the following formula can be used - 
M₁V₁ = M₂V₂ 
where , 
M₁ = concentration of acid , 
V₁ = volume of acid , 
M₂ = concentration of base, 
V₂ = volume of base . 
from , the question , 
M₁ = ? M 
V₁ = 8.0 mL 
M₂ = 2.0 M 
V₂ = 40 mL 
Using the above formula , the molarity of acid , can be calculated as , 
M₁V₁ = M₂V₂
M₁ * 8.0mL = 2.0 M * 40mL
M₁ = 10 M
Hence, the molarity of the acid = 10 M