A space-elevator cabin has reached a height of 640km above Earth’s surface and is accelerating upward at 2ms−2. Taking R=6.4×106m and g=9.8ms−2 at the surface, what is the reading of a weighing machine for an astronaut of mass 60kg inside the cabin?
(a) 708N
(b) 600N
(c) 486N
(d) 468N