In a tractor seat system, the chassis frequency and seat suspension damping rate are 20 rad s^-1 and 400 N m^-1 s, respectively. The critical damping rate of tractor seat system is 1600 N m^-1 s. If the combined mass of the seat and operator is 80 kg, the transmissibility of vibration is _______. (rounded off to 2 decimal places)