mm0wkj
My guess as follows,
APS 60,000kg
Traffic 20,000kg
Fuel 34,200kg
TTOM 114,200kg
Allowances:
Reserves: 5,000kg
C/T (un-useable) 500kg
Assumptions
Burn 3,500kg p/h
= Just under 8 ¼ hours flight time.
A 757-200 driver can answer you better though.
Bored