In a slab rolling operation, the maximum thickness reduction $(Δℎ_{max}$) is given by $Δ_{max}$ = $\mu^2R$ , where $R$ is the radius of the roll and $\mu$ is the coefficient of friction between the roll and the sheet. If $\mu$ = $0.1$, the maximum angle subtended by the deformation zone at the centre of the roll (bite angle in degrees) is _______