Refer to figure.
Take-off fuel (T/OFF FUEL) = Trip fuel + Contingency fuel (CONT) + Alternate (ALTN) + Final Reserve fuel (FINRES) + Extra fuel (EXTRA)

Therefore:
Final Reserve fuel (FINRES) = T/OFF FUEL - (TRIP + CONT + ALTN + EXTRA)

• In order to make the above calculation, we must determine the Contingency Fuel:

Fuel flow at holding speed is not given, therefore we will assume contingency to be 5% of trip fuel
Contingency Fuel = 5% x 15 320 kg = 766 kg

We can now calculate the Final reserve fuel:
Final Reserve fuel (FINRES) = 19 764 kg - (15 320 kg + 766 kg + 1504 kg + 1000 kg)
Final Reserve fuel (FINRES) = 1174 kg