A spring balance is calibrated at sea level where g=9.8ms−2. When it is taken to the top of a mountain 3km high, it still shows 50kg for a particular suitcase. Using R=6.4×106m, calculate the percentage error in the indicated mass due to the change in g.
(a) 0.10% more
(b) 0.05% less
(c) 0.10% less
(d) 0.94% less