A single slit of width b is illuminated by a coherent monochromatic light of wavelength \[\lambda \].If the second and fourth minima in the diffraction pattern at a distance 1 m from the slit are at 3 cm and 6 cm respectively from the central maximum, what is the width of the central maximum ? (i.e., distance between first minimum on either side of the central maximum) [JEE Online 08-04-2017]