Correct choice is (a) 4430kg
Easy explanation: Given crew weight = 150kg, payload weight = 600kg
Fuel weight fraction Wf / W0 = 1.06[1 – Wx/W0],
Now from fuel fraction method,
Wx / W0 = multiplication of each phase fraction
= 0.975*0.98*0.96*0.8*0.96*0.97
= 0.6833
Now,
Wf / W0 = 1.06 * [1 – (Wx / W0)] = 0.3357
Empty weight fraction We / W0 = 0.481
Gross weight of aircraft is,
W0 = Wcrew + Wpayload + Wfuel + Wempty
By re-arranging,
W0 = Wcrew + Wpayload / [1 – (Wf/ W0) – (We / W0)]
= 150 + 600 / [1-0.3357-0.495] = 4430kg