Physics-Single Silt Diffraction

In a single-slit diffraction pattern on a flat screen, the central bright fringe is 1.08 cm wide when the slit width is 3.40E-5 m. When the slit is replaced by a second slit, the wavelength of the light and the distance to the screen remaining unchanged, the central bright fringe broadens to a width of 1.80 cm. What is the width of the second slit? It may be assumed that θ is so small that sinθ ∼ tanθ

Can anyone show me how to do it?