In a single slit diffraction of light of wavelength $\mathrm{\lambda }$ by a slit of width e, the size of the central maximum on a screen at a distance b is 

• A

  $2\mathrm{b\lambda }+\mathrm{e}$

• B

  $\frac{2\mathrm{b\lambda }}{\mathrm{e}}$

• C

  $\frac{2\mathrm{b\lambda }}{\mathrm{e}}+\mathrm{e}$

• D

  $\frac{2\mathrm{b\lambda }}{\mathrm{e}}-\mathrm{e}$