A plane light wave with wavelength = 0.70m falls normally on the base of a biprism made

A plane light wave with wavelength λ = 0.70μm falls normally on the base of a biprism made of glass (n = 1.520) with refracting angle θ = 5.0°. Behind the biprism (Fig. 5.15) there is a plane-parallel plate, with the space between them filled up with benzene (n' = 1.500). Find the width of a fringe on the screen Sc placed behind this system.