Two slabs with square cross section of different materials \( (1, 2) \) with equal sides \( (l) \) and thickness \( d_{1} \) and \( d_{2} \) such that \( d_{2} = 2 d_{1} \) and \( l > d_{2} \). Considering lowest edges of these slabs are fixed to the floor, we apply equal shearing force on the narrow faces. The angle of deformation is \( \theta_{2} = 2 \theta_{1} \). If the shear moduli of material \( 1 \) is \( 4 \times 10^{9} \, \text{N} / \text{m}^{2} \), then shear moduli of material \( 2 \) is \( x \times 10^{9} \, \text{N} / \text{m}^{2} \), where value of \( x \) is _______.
