we know that
a = ω²r
r = 6380 km----------- > 6.38e6 m
ω=2π/86400 sec
a=(2π/86400) ² (6.38e6 m )------------
> 0.03374
a = 0.03374 m/sec²
if g------------------- > 9.8 m/sec²
X----------------------> 0.03374 m/sec²
X=0.03374 /9.8---------- > 0.00344
a = 0.00343 g
the answer is
a = 0.03374 m/sec²
a = 0.00343 g