according the computer all flap settings where available for the takeoff but flaps 20 was given as the optimum. The runway was 27 and the length 2000 metres with a wind 220 degress 19 gusting 31 and qnh 1009. zero fuel weight 74.9 and fuel 13,600. Heavy rain but airfield had no standing water. The question is for control in gusty conditions what flap setting would be the best ?