A 3-phase, 4-wire feeder is installed between a fused disconnect with 100A fuses and a MLO panelboard with listed 90 degree Celsius lugs. The termination rating of the fused disconnect is unknown. The feeder is installed in EMT that traverses the rooftop for a distance of 60 feet before entering a mechanical room. The average ambient temperature of the area of the install is 90 degrees F. The EMT is installed on 3.5" blocks. The feeder supplies a continuous load of 57.5 amps. What is the minimum XHHW-2 conductor that is permitted for this installation by the NEC?