Please help to solve this question:

Please help to solve this question:
Candle A and candle B are of the same length.Candle A,which is broader,can burn for 5 hours while Candle B,the thinner candle,can burn for 4 hours.If both candles are lighted at the same time,how long does it take for candle A to be twice as long left as candle
Working please,thank you.