In YDSE, find the thickness (in $\mathrm{\mu }$m) of a glass slab ($\mathrm{\mu }$ = 1.5) which should be placed before the upper slit S₁ so that the central maximum now lies at a point where 5th bright fringe was lying earlier (before inserting the slab). Wavelength of light used is 5000 $\text{Å}$.