According to the question,

 1 man = 2 women 

10 men = 20 women

∴ 10 men + 8 women 

⇒(20+8) women= 28 women

4 men + 6 women= (8+6) women 

                           =14 women

Here,

M₁ = 28, D₁ =5, W₂ =1

M₂ = 14, D₂ = ?, W₁ = 1

So according to the formula,

     M₁ D₁ W₂ = M₂ D₂ W₁

$$\begin{gathered} \Rightarrow 28\times 5\times 1=14\times D_2\times 1 \\ \therefore D_2=\frac{28\times 5}{14}=10 days \end{gathered}$$

Hence option B is correct.