Light consisting of two wavelengths (A1 = 633nm andA2 = 582 nm) is incident on a variable-width double slit. (The separation of the slits can be changed) A1 passes through a double slit of unknown separation and A2 passes through the double slit of separation 0.250 mm. The 4rth dark fringe (X4 ) for A2 is located at twice the distance from the central maximum compared with the distance of 5th bright fringe for A1. What is the unknown slit separation