What is the maximum bandwidth permitted by FCC rules for amateur radio stations transmitting on USB frequencies in the 60-meter band?

Explication

The 60 meter allocation is shared with federal fixed-service users, so the FCC holds every amateur emission there to 2.8 kHz, roughly the width of a normal SSB voice signal. Wider modes are not an option on the band even though 5.6 kHz would fit an AM signal.