A Gun metal sleeve is fixed securely to a steel shaft and the compound shaft is subjected to Torque. If the torque on the sleeve is twice that on the shaft. find the ratio of the external diameter of the sleeve to the diameter of the shaft (Round of 2 decimal place). Take τ_{Gun metal} = 45 MPa and τ_steel = 80 MPa and G_steel = 2.5 G_{Gun metal}