In young's double slit experiment a mixture of two lights of wavelengths 5000 $\stackrel{\text{o}}{\text{A}}$ and $\lambda$ is used. If is observed that the third dark fringe of 5000 $\stackrel{\text{o}}{\text{A}}$ coincides with third bright fringe of wavelength $\lambda$. Then find $\lambda$. 

• A

  4728.5 $\stackrel{\text{o}}{\text{A}}$

• B

  6532.7 $\stackrel{\text{o}}{\text{A}}$

• C

  4612.8 $\stackrel{\text{o}}{\text{A}}$

• D

  4166.66 $\stackrel{\text{o}}{\text{A}}$