Refer to CAP697 MRJT1 Figure 4.7.2 (One Engine Inop):An aircraft on an extended range operation is required never to be more than 120 minutes from an alternate, based on 1 engine inoperative LRC conditions in IS | ATPL

Question id 108 - Flight Planning and Monitoring - ATPL - Airline Transport Pilot license

Using the above table and a given mass of 40000 kg at the most critical point, the maximum air distance to the relevant alternate is: 810 NM

794 NM

875 NM

735 NM[see Annex]