Two candles of same height are lighted at the same time. The first is consumed in 3 hours and second in 2 hours. Assuming that each candles burns at a constant rate, in how many hours after being lighted, the ratio between the first and second candles becomes 2:1? A) 2 hour B) 2.5 hour C) 4 hour D) 1.5 hour E) None of these