A nigid flange coupling is used to transmi torque of 300Nm between two coaxial shafts each of diameter 30mm (d) The materials used for shaft flange and bolts are alloy steel, cast iron and steel respectively. Four bolts are used to couple the flanges. The shafts are keyed to the flange hub The permissible shear stress is 120MPa for the machine elements invoived ie bolts, shat and keys. Use standard design value of pitch circle diameter as sd. fiange thickness as 0.5d. Estimate the poli diameter in mm and permissible crushing stress in MPa [8M]