brns, that looks horribly familiar and I also got it wrong.
I think from memory that the 1-inop fuel requirement is the largest fuel load with reserves and comes to 20,320 kg.
From there subtract fuel from BRW to check MZFW and if ok then subtract BW to get PL. The figure I got here was 15,230 kg for payload but hey, I got it wrong so don't follow me.
