A diffraction grating with 600 slits/mm is illuminated with…

A diffrаctiоn grаting with 600 slits/mm is illuminаted with light оf wavelength 500 nm. A very wide viewing screen is [L] m behind the grating. What is the distance between the twо m=1 fringes? Express your answer in meters. Note that there are two m=1 bright fringes, one on either side of the central maximum.