Here,

M₁ = 10, D₁ =6, W₁ =40, T₁ = 3

M₂ = 12, D₂ = ?, W₂ = 16, T₂ = 8

So according to the formula,

     M₁ D₁ W₂ = M₂ D₂ W₁

$$\begin{gathered} \Rightarrow 10\times 6\times 3\times 40=12\times D_{2}8\times 16 \\ \therefore D_2=\frac{10\times 6\times 3\times 40}{12\times 8\times 16} \\ =\frac{75}{16}= 4\frac{11}{16}days \end{gathered}$$

Hence, option B is the correct.