Work out your fuel flow
using the latest ACTUAL information .... then use that fuel flow to predict your FUEL at the required
next point - in this case MIKE.
So...
ACTUAL TIME BETA (1:22) to GAMMA (1:47) = 25 mins
ACTUAL FUEL BETA (2760 kg) to GAMMA (2360 kg) = 400 kg
FUEL FLOW BETA to GAMMA = 400 / 25 = 16 kg / min
FUEL USED GAMMA to MIKE = 68 x 16 = 1088 kg
SO, FUEL AT MIKE = 2360 - 1088 = 1272 kg