Equal masses of two samples of charcoal `A and B` are burnt separately and the resulting carbon dioxide are collected in two vessels. The radioactivity of `^14 C` is measured for both the gas samples. The gas from the charcoal A gives `2100 counts` per week and the gas from the charcoal A gives 2100 counts per week and the gas from the charcoal `B` gives `1400` counts per week. Find the age difference between the two samples. Half-life of `^14 C = 5730 y`.